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Muslim scientist
Name: Abd al-Rahman al-Khazini
Title: Al-Khazini
Birth: 11th century
Death: 12th century
Ethnicity: Byzantine Greek
School tradition: Islamic science, Islamic physics, Islamic astronomy
Main interests: Science, physics, astronomy, biology, alchemy, mathematics, philosophy
Notable ideas: Experimental scientific method in mechanics; gravitational potential energy; gravity at a distance; distinction between force, mass and weight
Influences: Aristotle, Archimedes, Al-Quhi, Alhacen, Biruni, Omar Khayyam
Influenced: Gregory Choniades, Byzantine science, Islamic science

Abd al-Rahman al-Khazini (Arabic: عبدالرحمن الخزيني‎) (flourished 1115–1130) was a Greek Muslim scientist, astronomer, physicist, biologist, alchemist, mathematician and philosopher from Merv, then in the Khorasan province of Persia but now in Turkmenistan, who made important contributions to physics and astronomy.[1] He is considered the greatest scholar from Merv.[2]

Robert E. Hall wrote the following on al-Khazini:

"His hydrostatic balance can leave no doubt that as a maker of scientific instruments he is among the greatest of any time."[3]



Al-Khazini was a Byzantine Greek[4] slave of the Seljuq Turks, who was taken to Merv after the Seljuq victory over the Byzantine Emperor Romanus IV.[5] His master, al-Khazin, gave him the best possible education in mathematical and philosophical subjects. Al-Khazini was also a pupil of the famous Persian poet, mathematician, astronomer and philosopher Omar Khayyám (1048-1131), who was living in Merv at the time.[6]

Al-Khazini later became a mathematical practitioner under the patronage of the Selj court, under Sultan Ahmed Sanjar. Little else is known about his life, but it is known that he refused rewards and handed back 1000 dinars sent to him by the wife of an Emir, and that he usually lived on 3 dinars a year.[2]


Sinjaric Tables

Included in his astronomical treatise az-Zij as-Sanjarī or Sinjaric Tables, Al-Khazini gave a description of his construction of a 24 hour water clock designed for astronomical purposes, an early example of an astronomical clock, and the positions of 46 stars computed from the date given in the Almagest for the year 500 AH (1115-1116 CE). He also computed tables for the observation of celestial bodies at the latitude of Merv.[2][7][8]

Al-Khazini's Zij as-Sanjarī was later translated into Greek by Gregory Choniades in the 13th century and was studied in the Byzantine Empire.[9]

The Book of the Balance of Wisdom

Al-Khazini is better known for his contributions to physics in his treatise The Book of the Balance of Wisdom, completed in 1121, which remained an important part of Islamic physics. The book contains studies of the hydrostatic balance, its construction and uses, and the theories of statics and hydrostatics that lie behind it, as developed by his predecessors, his contemporaries, and himself.[10] It also contains descriptions on the instruments of his predecessors, including the araeometer of Pappus and the pycnometer flask of al-Biruni, as well as his own hydrostatic balance and specialized balances and steelyards.[11]

Al-Biruni and al-Khazini were the first to apply experimental scientific methods to the fields of statics and dynamics, particularly for determining specific weights, such as those based on the theory of balances and weighing. He and his Muslim predecessors unified statics and dynamics into the science of mechanics, and they combined the fields of hydrostatics with dynamics to give birth to hydrodynamics. They applied the mathematical theories of ratios and infinitesimal techniques, and introduced algebraic and fine calculation techniques into the field of statics. They were also the first to generalize the theory of the centre of gravity and the first to apply it to three-dimensional bodies. They also founded the theory of the ponderable lever and created the "science of gravity" which was later further developed in medieval Europe. The contributions of al-Khazini and his Muslim predecessors to mechanics laid the foundations for the later development of classical mechanics in Renaissance Europe.[12]

The first of the book's eight chapters deals with his predecessors' theories on the centre of gravity, including Al-Razi (Latinized as Rhazes), Abū Rayhān al-Bīrūnī, and Omar Khayyám. He also draws attention to the failure of the ancient Greeks to clearly differentiate between force, mass, and weight, and he goes on to show awareness of the weight of the air, and of its decrease in density with altitude.[13] The strict definition for a specific weight is given by Al-Khazini in The Book of the Balance of Wisdom:[13]

"The magnitude of weight of a small body of any substance is in the same ratio to its volume as the magnitude of weight of a larger body (of the same substance) to its volume."

After extensive experimentation, Al-Khazini records the specific gravities of fifty substances, including various stones, metals, liquids, salts, amber, and clay. The accuracy of his measures were impressive and comparable to modern values. In another experiment, Al-Khazini discovered that there was greater density of water when nearer to the Earth's centre, which was later proven by Roger Bacon in the 13th century.[14]

Al-Khazini defines heaviness in traditional Aristotelian terms as an inherent property of heavy bodies:

"A heavy body is one which is moved by an inherent force, constantly, towards the centre of the world. Suffice it to say, I mean that a heavy body is one which has a force moving it towards the central point, and constantly in the direction of the centre, without being moved by that force in any different direction; and that the force referred to is inherent in the body, not derived from without, nor separated from it-."[15]

On the basis that there is denser air when nearer to the centre of the Earth (derived from the Archimedes principle),[16] and that the weight of heavy bodies increase as they are farther from the centre of the Earth (derived from al-Quhi and Alhacen's theories that weight varies with the distance from the centre of the Earth), al-Khazini postulated that the gravity of a body varies with its distance from the centre of the Earth:[17]

"For each heavy body of a known weight positioned at a certain distance from the centre of the universe, its gravity depends on the remoteness from the centre of the universe. For that reason, the gravities of bodies relate as their distances from the centre of the universe. The farther is a body from the centre of the Universe, the heavier it is; the closer to the centre, the lighter it is. For that reason, the gravities of bodies relate as their distances from the centre of the Universe."[18][19]

It appears that what al-Khazini meant by "gravity" ("thiql" in Arabic) is both an idea similar to the modern concept of gravitational potential energy,[20] and the moment of a force relative to a point (both meanings were derived from al-Quhi and Alhacen).[21] In either case, al-Khazini appears to have been the first to propose that the gravity of a body varies with its distance from the centre of the Earth.[22] In his first sense of the word "gravity", the concept was not considered again until Newton's law of universal gravitation in the 18th century,[23][24] but in his second sense of the word, the concept was considered again by Jordanus de Nemore in the 13th century.[17][21]

N. Khanikoff, an early translator and commentator of al-Khazini's work, summarized his ideas regarding gravity as follows:

"But the ideas of the Arab philosophers with regard to gravitation are, in my opinion, much more remarkable; I will not call it universal gravitation, for our author expressly exempts the heavenly bodies from the influence of this force, but terrestrial gravitation. That this great law of nature did not present itself to their minds in the form of a mutual attraction of all existing bodies, as Newton enunciated it five centuries later, is quite natural, for at the time when the principles exhibited by our author were brought forward, the earth was still regarded as fixed immovably in the centre of the universe, and even the centrifugal force had not yet been discovered. But what is more astonishing is the fact that, having inherited from the Greeks the doctrine that all bodies are attracted toward the centre of the earth, and that this attraction acts in the direct ratio of the mass, having moreover not failed to perceive that attraction is a function of the distance of the bodies attracted from the centre of attraction, and having even been aware that, if the centre of the earth were surrounded by concentric spheres, all bodies of equal mass placed upon those spherical surfaces would press equally upon the same surfaces, and differently upon each sphere – that, in spite of all this, they held that weight was directly as the mass and the distance from the centre of the earth, without even suspecting, so far as it appears, that this attraction might be mutual between the body attracting and the bodies attracted, and that the law as enunciated by them was inconsistent with the principle which they admitted, that the containing surface of a liquid in equilibrium is a spherical surface."[25]

Treatise on Instruments

His Risala fi'l-alat (Treatise on Instruments) has seven parts describing different scientific instruments: the triquetrum, dioptra, a triangular instrument he invented, the quadrant and sextant, the astrolabe, and original instruments involving reflection.[26]

Alchemy and biology

Al-Khazini wrote the following on evolution in alchemy and biology, comparing the transmutation of elements with the transmutation of species, and how they were perceived by natural philosophers and common laymen in the medieval Islamic world at the time:

"When common people hear from natural philosophers that gold is a body which has attained to perfection of maturity, to the goal of completeness, they firmly believe that it is something which has gradually come to that perfection by passing through the forms of all other metallic bodies, so that its gold nature was originally lead, afterward it became tin, then brass, then silver, and finally reached the development of gold; not knowing that the natural philosophers mean, in saying this, only something like what they mean when they speak of man, and attribute to him a completeness and equilibrium in nature and constitution - not that man was once a bull, and was changed into an ass, and afterward into a horse, and after that into an ape, and finally became a man."[27]



  1. ^ Abd Al-Rahman Al-Khazini, Science and Its Times (2006). Thomson Gale.
  2. ^ a b c Zaimeche, p. 5.
  3. ^ Robert E. Hall (1973). "Al-Khazini", Dictionary of Scientific Biography, Vol. VII, p. 336.
  4. ^ Kennedy, Islamic Astronomical Tables, p. 7.
  5. ^ Klotz, "Multicultural Perspectives in Science Education: One Prescription for Failure".

    "Al-Khazini (who lived in the 12th century), a slave of the Selj Turks, but of Byzantine origin, probably one of the spoils of the victory of the Seljs over the Christian emperor of Constantinople, Romanus IV Diogenes."

  6. ^ Rosenfeld, p. 686-688.
  7. ^ Sarton, p. 565.
  8. ^ Kennedy, Islamic Astronomical Tables, pp. 7, 37-39
  9. ^ David Pingree (1964), "Gregory Chioniades and Palaeologan Astronomy", Dumbarton Oaks Papers 18, p. 135-160.
  10. ^ Mariam Rozhanskaya, "On a Mathematical Problem in al-Khazini's Book of the Balance of Wisdom", in David A. King and George Saliba, ed., Useful Reference Encyclopedia Deferent to Equant: A Volume of Studies in the History of Science in the Ancient and Medieval Near East in Honor of E. S. Kennedy, Annals of the New York Academy of Science, vol. 500 (1987), p. 427
  11. ^ Robert E. Hall (1973). "Al-Khazini", Dictionary of Scientific Biography, Vol. VII, p. 346.
  12. ^ Rozhanskaya and Levinova (1996), p. 642:

    "Numerous fine experimental methods were developed for determining the specific weight, which were based, in particular, on the theory of balances and weighing. The classical works of al-Biruni and al-Khazini can by right be considered as the beginning of the application of experimental methods in medieval science."

  13. ^ a b Hill, p. 61. (cf. Zaimeche, p. 5.)
  14. ^ Max Meyerhof (1931), "Science and Medicine", in Sir T. Arnold and A. Guillaume, Legacy of Islam, p. 342, Oxford University Press. (cf. Zaimeche, p. 7)
  15. ^ N. Khanikoff, ed. and trans., "Analysis and Extracts of ... Book of the Balance of Wisdom, An Arabic Work on the Water-Balance, Written by 'Al-Khâzinî in the Twelfth Century", chap. 1, sect. 1.2, Journal of the American Oriental Society, 6. (1858 - 1860): 1-128, at p. 26.
  16. ^ Marshall Clagett, The Science of Mechanics in the Middle Ages, (Madison, Univ. of Wisconsin Pr., 1961), pp. 65-68
  17. ^ a b Professor Mohammed Abattouy (2002), "The Arabic Science of weights: A Report on an Ongoing Research Project", The Bulletin of the Royal Institute for Inter-Faith Studies 4, p. 109-130:

    "For their parts, al-Quhi and Ibn al-Haytham had the priority in formulating the hypothesis that the heaviness of bodies vary with their distance from a specific point, the center of the earth. [...] In his rescensions of the works of his predecessors, al-Khazini pushed forward this idea and drew from it a spectacular conclusion regarding the variation of gravity with the distance from the centre of the world. All this work represented strong antecedents to the concept of positional weight (gravitas secundum sitam) formulated by Jordanus in the 13th century."

  18. ^ Rozhanskaya and Levinova (1996), p. 621-2 (cf. partial quotation at Zaimeche, p. 7).
  19. ^ Earlier translation, N. Khanikoff, ed. and trans., "Analysis and Extracts of ... Book of the Balance of Wisdom, An Arabic Work on the Water-Balance, Written by 'Al-Khâzinî in the Twelfth Century", chap. 5, sect. 3.1, Journal of the American Oriental Society, 6. (1858 - 1860): 1-128, at p. 36:

    "The weight of any heavy body, of known weight at a particular distance from the centre of the world, varies according to the variation of its distance therefrom; so that, as often as it is removed from the centre, it becomes heavier, and when brought nearer to it, is lighter. On this account, the relation of gravity to gravity is as the relation of distance to distance from the centre."

  20. ^ Rozhanskaya and Levinova (1996), p. 621:

    "According to al-Khazini, this variation of the gravity of a body with its distance from the 'centre of the universe' is associated with variations of density of the 'cosmos', i.e. the medium surrounding the Earth from the maximum at the Earth's surface to zero at the 'periphery' of the cosmos and vice versa. The 'gravity' of a body is understood here as a category similar to the modern concept of potential energy."

  21. ^ a b Rozhanskaya and Levinova (1996), p. 622.
  22. ^ Rozhanskaya and Levinova (1996), p. 622:

    "Thus, the author of Kitab mizan al-hikma was the first in the history of mechanics to propose the hypothesis that the gravities of bodies vary depending on their distances from the centre of the Earth. Neither of the medieval treatises known at present considered the problem."

  23. ^ Rozhanskaya and Levinova (1996), p. 622:

    "The phenomenon of variation of the gravity of bodies with variations of their distances from the centre of the Earth was discovered only in the eighteenth century after a certain development in the theory of gravitation.

  24. ^ Zaimeche, p. 7.
  25. ^ N. Khanikoff (1858-1860), ed. and trans., "Analysis and Extracts of ... Book of the Balance of Wisdom, An Arabic Work on the Water-Balance, Written by 'Al-Khâzinî in the Twelfth Century", Journal of the American Oriental Society 6: 1-128, at p. 39.
  26. ^ Robert E. Hall (1973). "Al-Biruni", Dictionary of Scientific Biography, Vol. VII, p. 338.
  27. ^ John William Draper (1878). History of the Conflict Between Religion and Science, p. 237. ISBN 1603030964.


  • Robert E. Hall (1973). "Al-Khazini", Dictionary of Scientific Biography, Vol. VII, p. 335-351*
  • Donald Routledge Hill (1993). Islamic Science and Engineering. Edinburgh University Press.
  • E. S. Kennedy (1956). "A Survey of Islamic Astronomical Tables", Transactions of the American Philosophical Society, New Series, 46 (2), Philadelphia.
  • Irving M. Klotz (1993). "Multicultural Perspectives in Science Education: One Prescription for Failure", Phi Delta Kappan 75.
  • Mariam Rozhanskaya and I. S. Levinova (1996), "Statics", in Roshdi Rashed, ed., Encyclopedia of the History of Arabic Science, Vol. 2, p. 614-642. Routledge, London and New York.
  • Boris Rosenfeld (1994), "Abu'l-Fath Abd al-Rahman al-Khazini (XII Century) by Mariam Mikhailovna Rozhanskaya", Isis 85 (4), p. 686-688.
  • George Sarton (1927), Introduction to the History of Science, Vol. I, The Carnegie Institution, Washington.
  • Salah Zaimeche PhD (2005). Merv, Foundation for Science Technology and Civilization.

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