Ibn al-Haytham was the first to correctly explain vision asintromissive rather than extramissive,[14] and to argue that vision occurs in the brain, pointing to observations that it is subjective and affected by personal experience.[15] He also stated the principle of least time for refraction which would later becomeFermat's principle.[16] He made major contributions to catoptrics and dioptrics by studying reflection, refraction and nature of images formed by light rays.[17][18] Ibn al-Haytham was an early proponent of the concept that a hypothesis must be supported by experiments based on confirmable procedures or mathematical reasoning – an early pioneer in thescientific method five centuries beforeRenaissance scientists,[19][20][21][22] he is sometimes described as the world's "first true scientist".[12] He was also apolymath, writing onphilosophy,theology andmedicine.[23]
Born inBasra, he spent most of his productive period in theFatimid capital ofCairo and earned his living authoring various treatises and tutoring members of the nobilities.[24] Ibn al-Haytham is sometimes given thebynameal-Baṣrī after his birthplace,[25] oral-Miṣrī ("the Egyptian").[26][27] Al-Haytham was dubbed the "SecondPtolemy" byAbu'l-Hasan Bayhaqi[28] and "The Physicist" byJohn Peckham.[29] Ibn al-Haytham paved the way for the modern science of physical optics.[30]
Biography
Abū ʿAlī al-Ḥasan ibn al-Ḥasan ibn al-Haytham (Alhazen) was born c. 965 to a family ofArab[9][31][32][33][34] orPersian[35][36][37][38][39] origin inBasra,Iraq, which was at the time part of theBuyid emirate. His initial influences were in the study of religion and service to the community. At the time, society had a number of conflicting views of religion that he ultimately sought to step aside from religion. This led to him delving into the study of mathematics and science.[40] He held a position with the title ofvizier in his native Basra, and became famous for his knowledge of applied mathematics, as evidenced by his attempt to regulate theflooding of the Nile.[41]
Upon his return to Cairo, he was given an administrative post. After he proved unable to fulfill this task as well, he contracted the ire of the caliphAl-Hakim,[42] and is said to have been forced into hiding until the caliph's death in 1021, after which his confiscated possessions were returned to him.[43]Legend has it that Alhazenfeigned madness and was kept under house arrest during this period.[44] During this time, he wrote his influentialBook of Optics. Alhazen continued to live in Cairo, in the neighborhood of the famousUniversity of al-Azhar, and lived from the proceeds of his literary production[45] until his death in c. 1040.[41] (A copy ofApollonius'Conics, written in Ibn al-Haytham's own handwriting exists inAya Sofya: (MS Aya Sofya 2762, 307 fob., dated Safar 415 A.H. [1024]).)[46]: Note 2
Alhazen's most famous work is his seven-volume treatise onopticsKitab al-Manazir (Book of Optics), written from 1011 to 1021.[48] In it, Ibn al-Haytham was the first to explain that vision occurs when light reflects from an object and then passes to one's eyes,[14] and to argue that vision occurs in the brain, pointing to observations that it is subjective and affected by personal experience.[15]
Optics wastranslated into Latin by an unknown scholar at the end of the 12th century or the beginning of the 13th century.[49][b]
This work enjoyed a great reputation during theMiddle Ages. The Latin version ofDe aspectibus was translated at the end of the 14th century into Italian vernacular, under the titleDe li aspecti.[50]
It was printed byFriedrich Risner in 1572, with the titleOpticae thesaurus: Alhazeni Arabis libri septem, nuncprimum editi; Eiusdem liber De Crepusculis et nubium ascensionibus (English: Treasury of Optics: seven books by the Arab Alhazen, first edition; by the same, on twilight and the height of clouds).[51]Risner is also the author of the name variant "Alhazen"; before Risner he was known in the west as Alhacen.[52]Works by Alhazen on geometric subjects were discovered in theBibliothèque nationale inParis in 1834 by E. A. Sedillot. In all, A. Mark Smith has accounted for 18 full or near-complete manuscripts, and five fragments, which are preserved in 14 locations, including one in theBodleian Library atOxford, and one in the library ofBruges.[53]
Front page of theOpticae Thesaurus, which included the first printed Latin translation of Alhazen'sBook of Optics. The illustration incorporates many examples of optical phenomena including perspective effects, the rainbow, mirrors, and refraction.
Two major theories on vision prevailed inclassical antiquity. The first theory, theemission theory, was supported by such thinkers asEuclid andPtolemy, who believed that sight worked by theeye emittingrays oflight. The second theory, theintromission theory supported byAristotle and his followers, had physical forms entering the eye from an object. Previous Islamic writers (such asal-Kindi) had argued essentially on Euclidean, Galenist, or Aristotelian lines. The strongest influence on theBook of Optics was from Ptolemy'sOptics, while the description of the anatomy and physiology of the eye was based on Galen's account.[54] Alhazen's achievement was to come up with a theory that successfully combined parts of the mathematical ray arguments of Euclid, the medical tradition ofGalen, and the intromission theories of Aristotle. Alhazen's intromission theory followed al-Kindi (and broke with Aristotle) in asserting that "from each point of every colored body, illuminated by any light, issue light and color along every straight line that can be drawn from that point".[55] This left him with the problem of explaining how a coherent image was formed from many independent sources of radiation; in particular, every point of an object would send rays to every point on the eye.
What Alhazen needed was for each point on an object to correspond to one point only on the eye.[55] He 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. He 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. As there was only one perpendicular ray that would enter the eye at any one point, and all these rays would converge on the centre of the eye in a cone, this allowed him to resolve the problem of each point on an object sending many rays to the eye; if only the perpendicular ray mattered, then he had a one-to-one correspondence and the confusion could be resolved.[56] He later asserted (in book seven of theOptics) that other rays would be refracted through the eye and perceivedas if perpendicular.[57] His arguments regarding perpendicular rays do not clearly explain whyonly perpendicular rays were perceived; why would the weaker oblique rays not be perceived more weakly?[58] His later argument that refracted rays would be perceived as if perpendicular does not seem persuasive.[59] However, despite its weaknesses, no other theory of the time was so comprehensive, and it was enormously influential, particularly in Western Europe. Directly or indirectly, hisDe Aspectibus (Book of Optics) inspired much activity in optics between the 13th and 17th centuries.Kepler's later theory of theretinal image (which resolved the problem of the correspondence of points on an object and points in the eye) built directly on the conceptual framework of Alhazen.[60]
Alhazen showed through experiment that light travels in straight lines, and carried out various experiments withlenses,mirrors,refraction, andreflection.[61] His analyses of reflection and refraction considered the vertical and horizontal components of light rays separately.[62]
Alhazen studied the process of sight, the structure of the eye, image formation in the eye, and thevisual system. Ian P. Howard argued in a 1996Perception article that Alhazen should be credited with many discoveries and theories previously attributed to Western Europeans writing centuries later. For example, he described what became in the 19th centuryHering's law of equal innervation. He wrote a description of verticalhoropters 600 years beforeAguilonius that is actually closer to the modern definition than Aguilonius's – and his work onbinocular disparity was repeated by Panum in 1858.[63] Craig Aaen-Stockdale, while agreeing that Alhazen should be credited with many advances, has expressed some caution, especially when considering Alhazen in isolation fromPtolemy, with whom Alhazen was extremely familiar. Alhazen corrected a significant error of Ptolemy regarding binocular vision, but otherwise his account is very similar; Ptolemy also attempted to explain what is now called Hering's law.[64] In general, Alhazen built on and expanded the optics of Ptolemy.[65]
In a more detailed account of Ibn al-Haytham's contribution to the study of binocular vision based on Lejeune[66] and Sabra,[67] Raynaud[68] showed that the concepts of correspondence, homonymous and crossed diplopia were in place in Ibn al-Haytham's optics. But contrary to Howard, he explained why Ibn al-Haytham did not give the circular figure of the horopter and why, by reasoning experimentally, he was in fact closer to the discovery of Panum's fusional area than that of the Vieth-Müller circle. In this regard, Ibn al-Haytham's theory of binocular vision faced two main limits: the lack of recognition of the role of the retina, and obviously the lack of an experimental investigation of ocular tracts.
Alhazen's most original contribution was that, after describing how he thought the eye was anatomically constructed, he went on to consider how this anatomy would behave functionally as an optical system.[69] His understanding ofpinhole projection from his experiments appears to have influenced his consideration of image inversion in the eye,[70] which he sought to avoid.[71] He maintained that the rays that fell perpendicularly on the lens (or glacial humor as he called it) 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.[72] He followedGalen in believing that thelens was the receptive organ of sight, although some of his work hints that he thought theretina was also involved.[73]
Alhazen's synthesis of light and vision adhered to the Aristotelian scheme, exhaustively describing the process of vision in a logical, complete fashion.[74]
Alhazen was the first physicist to give complete statement of the law of reflection.[75][76][77] He was first to state that the incident ray, the reflected ray, and the normal to the surface all lie in a same plane perpendicular to reflecting plane.[17][78]
His work oncatoptrics in Book V of the Book of Optics contains a discussion of what is now known as Alhazen's problem, first formulated byPtolemy in 150 AD. It comprises drawing lines from two points in theplane of a circle meeting at a point on thecircumference and making equal angles with thenormal at that point. This is equivalent to finding the point on the edge of a circularbilliard table at which a player must aim a cue ball at a given point to make it bounce off the table edge and hit another ball at a second given point. Thus, its main application in optics is to solve the problem, "Given a light source and a spherical mirror, find the point on the mirror where the light will be reflected to the eye of an observer." This leads to anequation of the fourth degree.[79] This eventually led Alhazen to derive a formula for the sum offourth powers, where previously only the formulas for the sums of squares and cubes had been stated. His method can be readily generalized to find the formula for the sum of any integral powers, although he did not himself do this (perhaps because he only needed the fourth power to calculate the volume of the paraboloid he was interested in). He used his result on sums of integral powers to perform what would now be called anintegration, where the formulas for the sums of integral squares and fourth powers allowed him to calculate the volume of aparaboloid.[80] Alhazen eventually solved the problem usingconic sections and a geometric proof. His solution was extremely long and complicated and may not have been understood by mathematicians reading him in Latin translation.Later mathematicians usedDescartes' analytical methods to analyse the problem.[81] An algebraic solution to the problem was finally found in 1965 by Jack M. Elkin, an actuarian.[82] Other solutions were discovered in 1989, by Harald Riede[83] and in 1997 by theOxford mathematicianPeter M. Neumann.[84][85]Recently,Mitsubishi Electric Research Laboratories (MERL) researchers solved the extension of Alhazen's problem to general rotationally symmetric quadric mirrors including hyperbolic, parabolic and elliptical mirrors.[86]
Camera obscura
Thecamera obscura was known to theancient Chinese, and was described by theHan ChinesepolymathShen Kuo in his scientific bookDream Pool Essays, published in the year 1088 C.E.Aristotle had discussed the basic principle behind it in hisProblems, but Alhazen's work contained the first clear description of camera obscura.[87] and early analysis[88] of the device.
Ibn al-Haytham used a camera obscura mainly to observe a partial solar eclipse.[89]In his essay, Ibn al-Haytham writes that he observed the sickle-like shape of the sun at the time of an eclipse. The introduction reads as follows: "The image of the sun at the time of the eclipse, unless it is total, demonstrates that when its light passes through a narrow, round hole and is cast on a plane opposite to the hole it takes on the form of a moonsickle."
It is admitted that his findings solidified the importance in the history of the camera obscura[90] but this treatise is important in many other respects.
Ancient optics and medieval optics were divided into optics and burning mirrors. Optics proper mainly focused on the study of vision, while burning mirrors focused on the properties of light and luminous rays.On the shape of the eclipse is probably one of the first attempts made by Ibn al-Haytham to articulate these two sciences.
Very often Ibn al-Haytham's discoveries benefited from the intersection of mathematical and experimental contributions. This is the case withOn the shape of the eclipse. Besides the fact that this treatise allowed more people to study partial eclipses of the sun, it especially allowed to better understand how the camera obscura works. This treatise is a physico-mathematical study of image formation inside the camera obscura. Ibn al-Haytham takes an experimental approach, and determines the result by varying the size and the shape of the aperture, the focal length of the camera, the shape and intensity of the light source.[91]
In his work he explains the inversion of the image in the camera obscura,[92] the fact that the image is similar to the source when the hole is small, but also the fact that the image can differ from the source when the hole is large. All these results are produced by using a point analysis of the image.[93]
In the seventh tract of his book of optics, Alhazen described an apparatus for experimenting with various cases of refraction, in order to investigate the relations between the angle of incidence, the angle of refraction and the angle of deflection. This apparatus was a modified version of an apparatus used by Ptolemy for similar purpose.[94][95][96]
Alhazen basically states the concept of unconscious inference in his discussion of colour before adding that the inferential step between sensing colour and differentiating it is shorter than the time taken between sensing and any other visible characteristic (aside from light), and that "time is so short as not to be clearly apparent to the beholder." Naturally, this suggests that the colour and form are perceived elsewhere. Alhazen goes on to say that information must travel to the central nerve cavity for processing and:
the sentient organ does not sense the forms that reach it from the visible objects untilafter it has been affected by these forms; thus it does not sense color as color or light as light until after it has been affected by the form of color or light. Now the affectation received by the sentient organ from the form of color or of light is a certain change; and change must take place in time; .....and it is in the time during which the form extends from the sentient organ's surface to the cavity of the common nerve, and in (the time) following that, that the sensitive faculty, which exists in the whole of the sentient body will perceive color as color...Thus the last sentient's perception of color as such and of light as such takes place at a time following that in which the form arrives from the surface of the sentient organ to the cavity of the common nerve.[97]
Alhazen explainedcolor constancy by observing that the light reflected from an object is modified by the object's color. He explained that the quality of the light and the color of the object are mixed, and the visual system separates light and color. In Book II, Chapter 3 he writes:
Again the light does not travel from the colored object to the eye unaccompanied by the color, nor does the form of the color pass from the colored object to the eye unaccompanied by the light. Neither the form of the light nor that of the color existing in the colored object can pass except as mingled together and the last sentient can onlyperceive them as mingled together. Nevertheless, the sentient perceives that the visible object is luminous and that the light seen in the object is other than the color and that these are two properties.[98]
Other contributions
TheKitab al-Manazir (Book of Optics) describes several experimental observations that Alhazen made and how he used his results to explain certain optical phenomena using mechanical analogies. He conducted experiments withprojectiles and concluded that only the impact ofperpendicular projectiles on surfaces was forceful enough to make them penetrate, whereas surfaces tended to deflectoblique projectile strikes. For example, to explain refraction from a rare to a dense medium, he used the mechanical analogy of an iron ball thrown at a thin slate covering a wide hole in a metal sheet. A perpendicular throw breaks the slate and passes through, whereas an oblique one with equal force and from an equal distance does not.[99] He also 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. The obvious answer to the problem of multiple rays and the eye was in the choice of the perpendicular ray, since only one such ray from each point on the surface of the object could penetrate the eye.[100]
Sudanese psychologist Omar Khaleefa has argued that Alhazen should be considered the founder ofexperimental psychology, for his pioneering work on the psychology of visual perception andoptical illusions.[101] Khaleefa has also argued that Alhazen should also be considered the "founder ofpsychophysics", a sub-discipline and precursor to modern psychology.[101] Although Alhazen made many subjective reports regarding vision, there is no evidence that he used quantitative psychophysical techniques and the claim has been rebuffed.[102]
Alhazen offered an explanation of theMoon illusion, an illusion that played an important role in the scientific tradition of medieval Europe.[103] Many authors repeated explanations that attempted to solve the problem of the Moon appearing larger near the horizon than it does when higher up in the sky. Alhazen argued against Ptolemy's refraction theory, and defined the problem in terms of perceived, rather than real, enlargement. He said that judging the distance of an object depends on there being an uninterrupted sequence of intervening bodies between the object and the observer. When the Moon is high in the sky there are no intervening objects, so the Moon appears close. The perceived size of an object of constant angular size varies with its perceived distance. Therefore, the Moon appears closer and smaller high in the sky, and further and larger on the horizon. Through works byRoger Bacon,John Pecham and Witelo based on Alhazen's explanation, the Moon illusion gradually came to be accepted as a psychological phenomenon, with the refraction theory being rejected in the 17th century.[104] Although Alhazen is often credited with the perceived distance explanation, he was not the first author to offer it.Cleomedes (c. 2nd century) gave this account (in addition to refraction), and he credited it toPosidonius (c. 135–50 BCE).[105] Ptolemy may also have offered this explanation in hisOptics, but the text is obscure.[106] Alhazen's writings were more widely available in the Middle Ages than those of these earlier authors, and that probably explains why Alhazen received the credit.
Therefore, the seeker after the truth is not one who studies the writings of the ancients and, following his natural disposition, puts his trust in them, but rather the one who suspects his faith in them and questions what he gathers from them, the one who submits to argument and demonstration, and not to the sayings of a human being whose nature is fraught with all kinds of imperfection and deficiency. 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.
An aspect associated with Alhazen's optical research is related to systemic and methodological reliance on experimentation (i'tibar)(Arabic: اختبار) andcontrolled testing in his scientific inquiries. Moreover, his experimental directives rested on combining classical physics (ilm tabi'i) with mathematics (ta'alim; geometry in particular). This mathematical-physical approach to experimental science supported most of his propositions inKitab al-Manazir (The Optics;De aspectibus orPerspectivae)[107] and grounded his theories of vision, light and colour, as well as his research in catoptrics anddioptrics (the study of the reflection and refraction of light, respectively).[108]
According to Matthias Schramm,[109] Alhazen "was the first to make a systematic use of the method of varying the experimental conditions in a constant and uniform manner, in an experiment showing that the intensity of the light-spot formed by the projection of themoonlight through two smallapertures onto a screen diminishes constantly as one of the apertures is gradually blocked up."[110] G. J. Toomer expressed some skepticism regarding Schramm's view,[111] partly because at the time (1964) theBook of Optics had not yet been fully translated from Arabic, and Toomer was concerned that without context, specific passages might be read anachronistically. While acknowledging Alhazen's importance in developing experimental techniques, Toomer argued that Alhazen should not be considered in isolation from other Islamic and ancient thinkers.[111] 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.[112]
Other works on physics
Optical treatises
Besides theBook of Optics, Alhazen wrote several other treatises on the same subject, including hisRisala fi l-Daw' (Treatise on Light). He investigated the properties ofluminance, therainbow,eclipses,twilight, andmoonlight. Experiments with mirrors and the refractive interfaces between air, water, and glass cubes, hemispheres, and quarter-spheres provided the foundation for his theories oncatoptrics.[113]
Celestial physics
Alhazen discussed thephysics of the celestial region in hisEpitome of Astronomy, arguing that Ptolemaic models must be understood in terms of physical objects rather than abstract hypotheses – in other words that it should be possible to create physical models where (for example) none of the celestial bodies would collide with each other. The suggestion of mechanical models for the Earth centredPtolemaic model "greatly contributed to the eventual triumph of the Ptolemaic system among the Christians of the West". Alhazen's determination to root astronomy in the realm of physical objects was important, however, because it meant astronomical hypotheses "were accountable to thelaws of physics", and could be criticised and improved upon in those terms.[114]
He also wroteMaqala fi daw al-qamar (On the Light of the Moon).
Mechanics
In his work, Alhazen discussed theories on themotion of a body.[113]
Astronomical works
On the Configuration of the World
In hisOn the Configuration of the World Alhazen presented a detailed description of the physical structure of the earth:
The earth as a whole is a round sphere whose center is the center of the world. It is stationary in its [the world's] middle, fixed in it and not moving in any direction nor moving with any of the varieties of motion, but always at rest.[115]
In hisAl-Shukūk ‛alā Batlamyūs, variously translated asDoubts Concerning Ptolemy orAporias against Ptolemy, published at some time between 1025 and 1028, Alhazen criticizedPtolemy'sAlmagest,Planetary Hypotheses, andOptics, pointing out various contradictions he found in these works, particularly in astronomy. Ptolemy'sAlmagest concerned mathematical theories regarding the motion of the planets, whereas theHypotheses concerned what Ptolemy thought was the actual configuration of the planets. Ptolemy himself acknowledged that his theories and configurations did not always agree with each other, arguing that this was not a problem provided it did not result in noticeable error, but Alhazen was particularly scathing in his criticism of the inherent contradictions in Ptolemy's works.[118] He considered that some of the mathematical devices Ptolemy introduced into astronomy, especially theequant, 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:[119]
Ptolemy assumed an arrangement (hay'a) that cannot exist, and the fact that this arrangement produces in his imagination the motions that belong to the planets does not free him from the error he committed in his assumed arrangement, for the existing motions of the planets cannot be the result of an arrangement that is impossible to exist... [F]or a man to imagine a circle in the heavens, and to imagine the planet moving in it does not bring about the planet's motion.[120]
Having pointed out the problems, Alhazen appears to have intended to resolve the contradictions he pointed out in Ptolemy in a later work. Alhazen believed there was a "true configuration" of the planets that Ptolemy had failed to grasp. He intended to complete and repair Ptolemy's system, not to replace it completely.[118] In theDoubts Concerning Ptolemy Alhazen set out his views on the difficulty of attaining scientific knowledge and the need to question existing authorities and theories:
Truth is sought for itself [but] the truths, [he warns] are immersed in uncertainties [and the scientific authorities (such as Ptolemy, whom he greatly respected) are] not immune from error...[67]
He held that the criticism of existing theories – which dominated this book – holds a special place in the growth of scientific knowledge.
Alhazen wrote a total of twenty-five astronomical works, some concerning technical issues such asExact Determination of the Meridian, a second group concerning accurate astronomical observation, a third group concerning various astronomical problems and questions such as the location of theMilky Way; Alhazen made the first systematic effort of evaluating the Milky Way's parallax, combining Ptolemy's data and his own. He concluded that the parallax is (probably very much) smaller than Lunar parallax, and the Milky way should be a celestial object. Though he was not the first who argued that the Milky Way does not belong to the atmosphere, he is the first who did quantitative analysis for the claim.[122]The fourth group consists of ten works on astronomical theory, including theDoubts andModel of the Motions discussed above.[123]
In elementary geometry, Alhazen attempted to solve the problem ofsquaring the circle using the area oflunes (crescent shapes), but later gave up on the impossible task.[130] The two lunes formed from aright triangle by erecting a semicircle on each of the triangle's sides, inward for the hypotenuse and outward for the other two sides, are known as thelunes of Alhazen; they have the same total area as the triangle itself.[131]
Number theory
Alhazen's contributions tonumber theory include his work onperfect numbers. In hisAnalysis and Synthesis, he may have been the first to state that every even perfect number is of the form 2n−1(2n − 1) where 2n − 1 isprime, but he was not able to prove this result;Euler later proved it in the 18th century, and it is now called theEuclid–Euler theorem.[130]
Alhazen solved problems involvingcongruences using what is now calledWilson's theorem. In hisOpuscula, Alhazen considers the solution of a system of congruences, and gives two general methods of solution. His first method, the canonical method, involved Wilson's theorem, while his second method involved a version of theChinese remainder theorem.[130]
Calculus
Alhazen discovered the sum formula for the fourth power, using a method that could be generally used to determine the sum for any integral power. He used this to find the volume of aparaboloid. He could find the integral formula for any polynomial without having developed a general formula.[132]
Other works
Influence of Melodies on the Souls of Animals
Alhazen also wrote aTreatise on the Influence of Melodies on the Souls of Animals, although no copies have survived. It appears to have been concerned with the question of whether animals could react to music, for example whether a camel would increase or decrease its pace.
Engineering
Inengineering, one account of his career as acivil engineer has him summoned to Egypt by the FatimidCaliph,Al-Hakim bi-Amr Allah, to regulate theflooding of theNile River. He carried out a detailed scientific study of the annualinundation of the Nile River, and he drew plans for building adam, at the site of the modern-dayAswan Dam. His field work, however, later made him aware of the impracticality of this scheme, and he soonfeigned madness so he could avoid punishment from the Caliph.[133]
Philosophy
In hisTreatise on Place, Alhazen disagreed withAristotle's view that nature abhors avoid, and he usedgeometry in an attempt to demonstrate that place (al-makan) is the imagined three-dimensional void between the inner surfaces of a containing body.[134]Abd-el-latif, a supporter of Aristotle's philosophical view of place, later criticized the work inFi al-Radd 'ala Ibn al-Haytham fi al-makan (A refutation of Ibn al-Haytham's place) for its geometrization of place.[134]
Alhazen also discussedspace perception and itsepistemological implications in hisBook of Optics. In "tying the visual perception of space to prior bodily experience, Alhazen unequivocally rejected the intuitiveness of spatial perception and, therefore, the autonomy of vision. Without tangible notions of distance and size forcorrelation, sight can tell us next to nothing about such things."[135]
Theology
Alhazen was a Muslim and most sources report that he was a Sunni and a follower of theAsh'ari school.[136][137][138][139]Ziauddin Sardar says that some of the greatestMuslim scientists, such as Ibn al-Haytham andAbū Rayhān al-Bīrūnī, who were pioneers of thescientific method, were themselves followers of the Ashʿari school of Islamic theology.[138] Like other Ashʿarites who believed that faith ortaqlid should apply only to Islam and not to any ancientHellenistic authorities,[140] Ibn al-Haytham's view thattaqlid should apply only toprophets of Islam and not to any other authorities formed the basis for much of hisscientific skepticism and criticism againstPtolemy and other ancient authorities in hisDoubts Concerning Ptolemy andBook of Optics.[141]
Alhazen wrote a work on Islamic theology in which he discussed prophethood and developed a system of philosophical criteria to discern its false claimants in his time.[142]He also wrote a treatise entitledFinding the Direction of Qibla by Calculation in which he discussed finding theQibla, where prayers (salat) are directed towards, mathematically.[143]
There are occasional references to theology or religious sentiment in his technical works, e.g.inDoubts Concerning Ptolemy:
Truth is sought for its own sake ... Finding the truth is difficult, and the road to it is rough. For the truths are plunged in obscurity. ... God, however, has not preserved the scientist from error and has not safeguarded science from shortcomings and faults. If this had been the case, scientists would not have disagreed upon any point of science...[144]
InThe Winding Motion:
From the statements made by the noble Shaykh, it is clear that he believes in Ptolemy's words in everything he says, without relying on a demonstration or calling on a proof, but by pure imitation (taqlid); that is how experts in the prophetic tradition have faith in Prophets, may the blessing of God be upon them. But it is not the way that mathematicians have faith in specialists in the demonstrative sciences.[145]
Regarding the relation of objective truth and God:
I constantly sought knowledge and truth, and it became my belief that for gaining access to the effulgence and closeness to God, there is no better way than that of searching for truth and knowledge.[146]
Alhazen made significant contributions to optics, number theory, geometry, astronomy and natural philosophy. Alhazen's work on optics is credited with contributing a new emphasis on experiment.
H. J. J. Winter, a British historian of science, summing up the importance of Ibn al-Haytham in the history ofphysics wrote:
After the death of Archimedes no really great physicist appeared until Ibn al-Haytham. If, therefore, we confine our interest only to the history of physics, there is a long period of over twelve hundred years during which the Golden Age of Greece gave way to the era of Muslim Scholasticism, and the experimental spirit of the noblest physicist of Antiquity lived again in the Arab Scholar from Basra.[157]
Over forty years previously,Jacob Bronowski presented Alhazen's work in a similar television documentary (and the corresponding book),The Ascent of Man. In episode 5 (The Music of the Spheres), Bronowski remarked that in his view, Alhazen was "the one really original scientific mind that Arab culture produced", whose theory of optics was not improved on till the time of Newton and Leibniz.
UNESCO declared 2015 theInternational Year of Light and its Director-General Irina Bokova dubbed Ibn al-Haytham 'the father of optics'.[163] Amongst others, this was to celebrate Ibn Al-Haytham's achievements in optics, mathematics and astronomy. An international campaign, created by the1001 Inventions organisation, titled1001 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.[164] The campaign also produced and released the short educational film1001 Inventions and the World of Ibn Al-Haytham.
Ibn al-Haytham appears on the 10,000 dinar banknote of theIraqi dinar, series 2003.[165]
List of works
According to medieval biographers, Alhazen wrote more than 200 works on a wide range of subjects, of which at least 96 of his scientific works are known. Most of his works are now lost, but more than 50 of them have survived to some extent. Nearly half of his surviving works are on mathematics, 23 of them are on astronomy, and 14 of them are on optics, with a few on other subjects.[166] Not all his surviving works have yet been studied, but some of the ones that have are given below.[167]
Treatise on the Influence of Melodies on the Souls of Animals (تأثير اللحون الموسيقية في النفوس الحيوانية)
كتاب في تحليل المسائل الهندسية (A book in engineering analysis)
الجامع في أصول الحساب (The whole in the assets of the account)
قول فی مساحة الکرة (Say in the sphere)
القول المعروف بالغریب فی حساب المعاملات (Saying the unknown in the calculation of transactions)
خواص المثلث من جهة العمود (Triangle properties from the side of the column)
رسالة فی مساحة المسجم المکافی (A message in the free space)
شرح أصول إقليدس (Explain the origins of Euclid)
المرايا المحرقة بالقطوع (The burning mirrors of the rainbow)
مقالة في القرصتن (Treatise on Centers of Gravity)
Lost works
A Book in which I have Summarized the Science of Optics from the Two Books of Euclid and Ptolemy, to which I have added the Notions of the First Discourse which is Missing from Ptolemy's Book[170]
Treatise on Burning Mirrors
Treatise on the Nature of [the Organ of] Sight and on How Vision is Achieved Through It
^/ælˈhæzən/; full nameAbū ʿAlī al-Ḥasan ibn al-Ḥasan ibn al-Haythamأبو علي، الحسن بن الحسن بن الهيثم;
^ A. Mark Smith has determined that there were at least two translators, based on their facility with Arabic; the first, more experienced scholar began the translation at the beginning of Book One, and handed it off in the middle of Chapter Three of Book Three.Smith 200191 Volume 1: Commentary and Latin text pp.xx–xxi. See also his 2006, 2008, 2010 translations.
^El-Bizri 2010, p. 11: "Ibn al-Haytham's groundbreaking studies in optics, including his research in catoptrics and dioptrics (respectively the sciences investigating the principles and instruments pertaining to the reflection and refraction of light), were principally gathered in his monumental opus: Kitåb al-manåóir (The Optics; De Aspectibus or Perspectivae; composed between 1028 CE and 1038 CE)."
^Rooney 2012, p. 39: "As a rigorous experimental physicist, he is sometimes credited with inventing the scientific method."
^Baker 2012, p. 449: "As shown earlier, Ibn al-Haytham was among the first scholars to experiment with animal psychology.
^AlsoAlhacen,Avennathan,Avenetan, etc.; the identity of "Alhazen" with Ibn al-Haytham al-Basri "was identified towards the end of the 19th century". (Vernet 1996, p. 788)
^Esposito, John L. (2000).The Oxford History of Islam. Oxford University Press. p. 192.: "Ibn al-Haytham (d. 1039), known in the West as Alhazan, was a leading Arab mathematician, astronomer, and physicist. His optical compendium, Kitab al-Manazir, is the greatest medieval work on optics."
^abFor the description of his main fields, see e.g.Vernet 1996, p. 788 ("He is one of the principal Arab mathematicians and, without any doubt, the best physicist.")Sabra 2008,Kalin, Ayduz & Dagli 2009 ("Ibn al-Ḥaytam was an eminent eleventh-century Arab optician, geometer, arithmetician, algebraist, astronomer, and engineer."),Dallal 1999 ("Ibn al-Haytham (d. 1039), known in the West as Alhazan, was a leading Arab mathematician, astronomer, and physicist. His optical compendium, Kitab al-Manazir, is the greatest medieval work on optics.")
^Roshdi Rashed,Ibn al-Haytham's Geometrical Methods and the Philosophy of Mathematics: A History of Arabic Sciences and Mathematics, Volume 5, Routledge (2017), p. 635
^"Alhazen Arab mathematician and physicist who was born around 965 in what is now Iraq." Critical Companion to Chaucer: A Literary Reference to His Life and Work
^Esposito (2000)، The Oxford History of Islam، Oxford University Press، p. 192. : "Ibn al-Haytham (d. 1039), known in the West as Alhazan, was a leading Arab mathematician, astronomer, and physicist. His optical compendium, Kitab al-Manazir, is the greatest medieval work on optics"
^(Child, Shuter & Taylor 1992, p. 70), (Dessel, Nehrich & Voran 1973, p. 164),Understanding History by John Child, Paul Shuter, David Taylor, p. 70. "Alhazen, a Persian scientist, showed that the eye saw light from other objects. This started optics, the science of light. The Arabs also studied astronomy, the study of the stars. "
^Enrico Narducci (1871). "Nota intorno ad una traduzione italiana fatta nel secolo decimoquarto del trattato d'ottica d'Alhazen".Bollettino di Bibliografia e di Storia delle Scienze Matematiche e Fisiche.4:1–40.. On this version, seeRaynaud 2020, pp. 139–153.
^Kelley, Milone & Aveni 2005, p. 83: "The first clear description of the device appears in theBook of Optics of Alhazen."
^Wade & Finger 2001: "The principles of the camera obscura first began to be correctly analysed in the eleventh century, when they were outlined by Ibn al-Haytham."
^German physicist Eilhard Wiedemann first provided an abridged German translation ofOn the shape of the eclipse:Eilhard Wiedemann (1914). "Über der Camera obscura bei Ibn al Haiṭam".Sitzungsberichte phys.-med. Sozietät in Erlangen.46:155–169. The work is now available in full:Raynaud 2016.
^Eder, Josef (1945).History of Photography. New York: Columbia University Press. p. 37.
^G. J. Toomer.Review at Toomer's 1964 review of Matthias Schramm (1963)Ibn Al-Haythams Weg Zur PhysikArchived 26 March 2017 at theWayback Machine Toomer p. 464: "Schramm sums up [Ibn Al-Haytham's] achievement in the development of scientific method.", p. 465: "Schramm has demonstrated .. beyond any dispute that Ibn al-Haytham is a major figure in the Islamic scientific tradition, particularly in the creation of experimental techniques." p. 465: "Only when the influence of ibn al-Haytam and others on the mainstream of later medieval physical writings has been seriously investigated can Schramm's claim that ibn al-Haytam was the true founder of modern physics be evaluated."
^Faruqi 2006, pp. 395–396:In seventeenth century Europe the problems formulated by Ibn al-Haytham (965–1041) became known as 'Alhazen's problem'. ... Al-Haytham's contributions to geometry and number theory went well beyond the Archimedean tradition. Al-Haytham also worked on analytical geometry and the beginnings of the link between algebra and geometry. Subsequently, this work led in pure mathematics to the harmonious fusion of algebra and geometry that was epitomised by Descartes in geometric analysis and by Newton in the calculus. Al-Haytham was a scientist who made major contributions to the fields of mathematics, physics and astronomy during the latter half of the tenth century.
^Katz 1998, p. 269: "In effect, this method characterised parallel lines as lines always equidistant from one another and also introduced the concept of motion into geometry."
^Ishaq, Usep Mohamad, and Wan Mohd Nor Wan Daud. "Tinjauan biografi-bibliografi Ibn al-haytham." Historia : Jurnal Program Studi Pendidikan Sejarah 5.2 (2017): 107–124.
^Kaminski, Joseph J. "The Trajectory of the Development of Islamic Thought – A Comparison Between Two Earlier and Two Later Scholars."The Contemporary Islamic Governed State. Palgrave Macmillan, Cham, 2017. 31–70. "For example, Ibn al-Haytham and Abū Rayhān al-Bīrūnī were among the most important medieval scholars who used the scientific method in their approach to natural science, and they were both Ash'arites"
^Sabra 2007, pp. 122, 128–129. & Grant 1974, p. 392 notes theBook of Optics has also been denoted asOpticae Thesaurus Alhazen Arabis, asDe Aspectibus, and also asPerspectiva
^Authier 2013, p. 23: "Alhazen's works in turn inspired many scientists of the Middle Ages, such as the English bishop, Robert Grosseteste (c. 1175–1253), and the English Franciscan, Roger Bacon (c. 1214–1294), Erazmus Ciolek Witelo, or Witelon (c. 1230* 1280), a Silesian-born Polish friar, philosopher and scholar, published in c. 1270 a treatise on optics, Perspectiva, largely based on Alhazen's works."
^Magill & Aves 1998, p. 66: "Roger Bacon, John Peckham, and Giambattista della Porta are only some of the many thinkers who were influenced by Alhazen's work."
^Zewail & Thomas 2010, p. 5: "The Latin translation of Alhazen's work influenced scientists and philosophers such as (Roger) Bacon and da Vinci, and formed the foundation for the work by mathematicians like Kepler, Descartes and Huygens..."
^El-Bizri 2010, p. 12: "This [Latin] version of Ibn al-Haytham's Optics, which became available in print, was read and consulted by scientists and philosophers of the caliber of Kepler, Galileo, Descartes, and Huygens as discussed byNader El-Bizri."
^Magill & Aves 1998, p. 66: "Sabra discusses in detail the impact of Alhazen's ideas on the optical discoveries of such men as Descartes and Christiaan Huygens; see alsoEl-Bizri 2005a."
^Magill & Aves 1998, p. 66: "Even Kepler, however, used some of Alhazen's ideas, for example, the one-to-one correspondence between points on the object and points in the eye. It would not be going too far to say that Alhazen's optical theories defined the scope and goals of the field from his day to ours."
^Ibn Al-Haytham, W. 'Arafat and H. J. J. Winter (1971)JSTOR4025317 (c. 1027–1038) The Light of the Stars: A Short Discourse by Ibn Al-HaythamAl-Haytham, Ibn; 'Arafat, W.; Winter, H. J. J. (1971)."The Light of the Stars: A Short Discourse by Ibn Al-Haytham".The British Journal for the History of Science.5 (3):282–288.doi:10.1017/S0007087400011237.JSTOR4025317. Archived from the original on 21 September 2022. Retrieved21 September 2022.{{cite journal}}: CS1 maint: bot: original URL status unknown (link)The British Journal for the History of Science Vol.5, No. 3 (Jun., 1971), pp. 282–288
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Further reading
Primary
Sabra, A. I, ed. (1983),The Optics of Ibn al-Haytham, Books I–II–III: On Direct Vision. The Arabic text, edited and with Introduction, Arabic-Latin Glossaries and Concordance Tables, Kuwait: National Council for Culture, Arts and Letters
Sabra, A. I, ed. (2002),The Optics of Ibn al-Haytham. Edition of the Arabic Text of Books IV–V: On Reflection and Images Seen by Reflection. 2 vols, Kuwait: National Council for Culture, Arts and Letters
El-Bizri, Nader (2009b), "Ibn al-Haytham et le problème de la couleur",Oriens Occidens,7 (1), Paris:CNRS:201–226
El-Bizri, Nader (2016), "Grosseteste's Meteorological Optics: Explications of the Phenomenon of the Rainbow after Ibn al-Haytham", in Cunningham, Jack P.; Hocknull, Mark (eds.),Robert Grosseteste and the Pursuit of Religious and Scientific Knowledge in the Middle Ages, Studies in the History of Philosophy of Mind, vol. 18, Dordrecht: Springer, pp. 21–39,ISBN978-3-319-33466-0
Graham, Mark.How Islam Created the Modern World. Amana Publications, 2006.
Omar, Saleh Beshara (June 1975),Ibn al-Haytham and Greek optics: a comparative study in scientific methodology, PhD Dissertation,University of Chicago, Department of Near Eastern Languages and Civilizations
Roshdi Rashed, Optics and Mathematics: Research on the history of scientific thought in Arabic, Variorum reprints, Aldershot, 1992.
Roshdi Rashed, Geometry and Dioptrics the tenth century: Ibn Sahl al-Quhi and Ibn al-Haytham (in French), Les Belles Lettres, Paris, 1993
Siegfried Zielinski & Franziska Latell,How One Sees, in: Variantology 4. On Deep Time Relations of Arts, Sciences and Technologies in the Arabic-Islamic World and Beyond, ed. by Siegfried Zielinski and Eckhard Fürlus in cooperation with Daniel Irrgang and Franziska Latell (Cologne: Verlag der Buchhandlung Walther König, 2010), pp. 19–42.Buchhandlung Walther-König - KWB 45: Variantology 4
