I've been waiting patiently to make this pick, but I'm not going to chance letting him slide any farther. We've had many fine scientists picked so far, but I'm not sure that any, including Newton, have a stronger case for the top spot than my pick. His work and advances in the fields of Physics, Mathematics, and Astronomy alone would place in the top tier. What sets him apart for me is his pioneering of the Scientific Method, which is absolutely foundational to modern science and has contributed to virtually every major scientific advance for the past millennium. It's hard to even do a full write up of his legacy without massive spotlighting, but I did my best to clean up a brief section of the article below. Just visit the wiki page to be fully blown away by the scope of his accomplishments.
Alhazen - Scientist
Abū ʿAlī al-Ḥasan ibn al-Ḥasan ibn al-Haytham (Arabic: ابو علی، حسن بن حسن بن الهيثم, Persian: ابن هیثم, Latinized: Alhacen or (deprecated) Alhazen) (965 in Basra - c. 1039 in Cairo), was an Arab[2] or Persian[3] polymath.[4] He made significant contributions to the principles of optics, as well as to anatomy, astronomy, engineering, mathematics, medicine, ophthalmology, philosophy, physics, psychology, visual perception, and to science in general with his introduction of the scientific method. He is sometimes called al-Basri (Arabic: البصري), after his birthplace in the city of Basra.[5]
Born circa 965, in Basra, Iraq and part of Buyid Persia at that time,[1] he lived mainly in Cairo, Egypt, dying there at age 76.[6] Over-confident about practical application of his mathematical knowledge, he assumed that he could regulate the floods of the Nile.[8] After being ordered by Al-Hakim bi-Amr Allah, the sixth ruler of the Fatimid caliphate, to carry out this operation, he quickly perceived the impossibility of what he was attempting to do, and retired from engineering. Fearing for his life, he feigned madness[1][9] and was placed under house arrest, during and after which he devoted himself to his scientific work until his death.[6]
Ibn al-Haytham is regarded as the "father of modern optics"[10] for his influential Book of Optics (written while he was under house arrest), which proved the intromission theory of vision and refined it into essentially its modern form. He is also recognized so for his experiments on optics, including experiments on lenses, mirrors, refraction, reflection, and the dispersion of light into its constituent colours.[11] He studied binocular vision and the Moon illusion, described the finite speed[12][13] of light, and argued that it is made of particles[14] travelling in straight lines.[13][15] Due to his formulation of a modern quantitative and empirical approach to physics and science, he is considered the pioneer of the modern scientific method[16][17] and the originator of the experimental nature of physics[18] and science.[19] Author Bradley Steffens describes him as the "first scientist".[20] He is also considered by A. I. Sabra to be the founder of experimental psychology[21] for his approach to visual perception and optical illusions,[22] and a pioneer of the philosophical field of phenomenology or the study of consciousness from a first-person perspective. His Book of Optics has been ranked with Isaac Newton's Philosophiae Naturalis Principia Mathematica as one of the most influential books in the history of physics,[23] for starting a revolution in optics[24] and visual perception.[25]
Ibn al-Haytham's achievements include many advances in physics and mathematics. He gave the first clear description[26] and correct analysis[27] of the camera obscura. He enunciated xxxxxxx's principle of least time and the concept of inertia (Newton's first law of motion),[28] and developed the concept of momentum.[29] He described the attraction between masses and was aware of the magnitude of acceleration due to gravity at-a-distance.[30] He stated that the heavenly bodies were accountable to the laws of physics and also presented a critique and reform of xxxxxxxx astronomy. He was the first to state xxxxxxxx's theorem in number theory, and he formulated the xxxxxxxxx quadrilateral[31] and a concept similar to xxxxxxxx's axiom[32] now used in non-Euclidean geometry. Moreover, he formulated and solved Alhazen's problem geometrically using early ideas related to calculus and mathematical induction.[33]
Scientific method
Neuroscientist Rosanna Gorini notes that "according to the majority of the historians al-Haytham was the pioneer of the modern scientific method."[16][71] Ibn al-Haytham developed rigorous experimental methods of controlled scientific testing to verify theoretical hypotheses and substantiate inductive conjectures.[30] Ibn al-Haytham's scientific method was very similar to the modern scientific method and consisted of the following procedures:[72]
1. Observation
2. Statement of problem
3. Formulation of hypothesis
4. Testing of hypothesis using experimentation
5. Analysis of experimental results
6. Interpretation of data and formulation of conclusion
7. Publication of findings
Other Important Discoveries/Observations:
Chapters 15–16 of the Book of Optics covered astronomy. Ibn al-Haytham was the first to discover that the celestial spheres do not consist of solid matter. He also discovered that the heavens are less dense than the air.
He built the first camera obscura and pinhole camera [27],
He maintained that a body moves perpetually unless an external force stops it or changes its direction of motion.[30] This was similar to the concept of inertia, but was largely a hypotheses that was not verified by experimentation. The key breakthrough in classical mechanics, the introduction of frictional force, was eventually made centuries later by Galileo Galilei, and then formulated as Newton's first law of motion.
His reformed empirical model was the first to reject the equant[94] and eccentrics,[95] separate natural philosophy from astronomy, free celestial kinematics from cosmology, and reduce physical entities to geometric entities. The model also propounded the Earth's rotation about its axis,[96] and the centres of motion were geometric points without any physical significance.
In geometry, Ibn al-Haytham developed analytical geometry and established a link between algebra and geometry.[106] Ibn al-Haytham also discovered a formula for adding the first 100 natural numbers (which may later have been intuited by Carl Friedrich Gauss as a youth). Ibn al-Haytham used a geometric proof to prove the formula.
His contributions to number theory includes his work on perfect numbers. In his Analysis and Synthesis, Ibn al-Haytham was the first to realize that every even perfect number is of the form 2n−1(2n − 1) where 2n − 1 is prime, but he was not able to prove this result successfully (xxxxxxx later proved it in the 18th century).