30 Facts About Ibn Al-Haytham

Hasan Ibn al-Haytham, Latinized as Alhazen, was an Arab mathematician, astronomer, and physicist of the Islamic Golden Age.

Ibn Al-Haytham was a polymath, writing on philosophy, theology and medicine.

Ibn Al-Haytham was dubbed the "Second Ptolemy" by Abu'l-Hasan Bayhaqi and "The Physicist" by John Peckham.

Ibn Al-Haytham held a position with the title vizier in his native Basra, and made a name for himself on his knowledge of applied mathematics.

However, Ibn al-Haytham was forced to concede the impracticability of his project.

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Ibn Al-Haytham attempted to resolve this by asserting that the eye would only perceive perpendicular rays from the object—for any one point on the eye, only the ray that reached it directly, without being refracted by any other part of the eye, would be perceived.

Ibn Al-Haytham argued, using a physical analogy, that perpendicular rays were stronger than oblique rays: in the same way that a ball thrown directly at a board might break the board, whereas a ball thrown obliquely at the board would glance off, perpendicular rays were stronger than refracted rays, and it was only perpendicular rays which were perceived by the eye.

Ibn Al-Haytham later asserted that other rays would be refracted through the eye and perceived as if perpendicular.

Ibn Al-Haytham assumed ray of light was radiated from specific points on the surface.

Ibn Al-Haytham wrote a description of vertical horopters 600 years before Aguilonius that is actually closer to the modern definition than Aguilonius's—and his work on binocular disparity was repeated by Panum in 1858.

Ibn Al-Haytham maintained that the rays that fell perpendicularly on the lens were further refracted outward as they left the glacial humor and the resulting image thus passed upright into the optic nerve at the back of the eye.

Ibn Al-Haytham followed Galen in believing that the lens was the receptive organ of sight, although some of his work hints that he thought the retina was involved.

Toomer concluded his review by saying that it would not be possible to assess Schramm's claim that Ibn al-Haytham was the true founder of modern physics without translating more of Alhazen's work and fully investigating his influence on later medieval writers.

Ibn Al-Haytham used his result on sums of integral powers to perform what would now be called an integration, where the formulas for the sums of integral squares and fourth powers allowed him to calculate the volume of a paraboloid.

Ibn Al-Haytham conducted experiments with projectiles and concluded that only the impact of perpendicular projectiles on surfaces was forceful enough to make them penetrate, whereas surfaces tended to deflect oblique projectile strikes.

Ibn Al-Haytham used this result to explain how intense, direct light hurts the eye, using a mechanical analogy: Alhazen associated 'strong' lights with perpendicular rays and 'weak' lights with oblique ones.

Ibn Al-Haytham said that judging the distance of an object depends on there being an uninterrupted sequence of intervening bodies between the object and the observer.

Ibn Al-Haytham investigated the properties of luminance, the rainbow, eclipses, twilight, and moonlight.

Ibn Al-Haytham considered that some of the mathematical devices Ptolemy introduced into astronomy, especially the equant, failed to satisfy the physical requirement of uniform circular motion, and noted the absurdity of relating actual physical motions to imaginary mathematical points, lines and circles:.

Ibn Al-Haytham intended to complete and repair Ptolemy's system, not to replace it completely.

Ibn Al-Haytham held that the criticism of existing theories—which dominated this book—holds a special place in the growth of scientific knowledge.

Ibn Al-Haytham kept a geocentric universe and assumed that celestial motions are uniformly circular, which required the inclusion of epicycles to explain observed motion, but he managed to eliminate Ptolemy's equant.

Ibn Al-Haytham concluded that the parallax is smaller than Lunar parallax, and the Milky way should be a celestial object.

Ibn Al-Haytham developed a formula for summing the first 100 natural numbers, using a geometric proof to prove the formula.

Ibn Al-Haytham formulated the Lambert quadrilateral, which Boris Abramovich Rozenfeld names the "Ibn al-Haytham–Lambert quadrilateral".

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Ibn Al-Haytham could find the integral formula for any polynomial without having developed a general formula.

Ibn Al-Haytham carried out a detailed scientific study of the annual inundation of the Nile River, and he drew plans for building a dam, at the site of the modern-day Aswan Dam.

Ibn Al-Haytham wrote a treatise entitled Finding the Direction of Qibla by Calculation in which he discussed finding the Qibla, where prayers are directed towards, mathematically.

Ibn Al-Haytham made the observation that the ratio between the angle of incidence and refraction does not remain constant, and investigated the magnifying power of a lens.

An international campaign, created by the 1001 Inventions organisation, titled 1001 Inventions and the World of Ibn Al-Haytham featuring a series of interactive exhibits, workshops and live shows about his work, partnering with science centers, science festivals, museums, and educational institutions, as well as digital and social media platforms.