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

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


Al-Khazini was a Byzantine Greek slave of the Seljuq Turks, who was taken to Merv after the Seljuq victory over the Byzantine Emperor Romanus IV. 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.

Al-Khazini later became a mathematical practitioner under the patronage of the Seljuk 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.


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.

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.

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. 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.

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.

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. The strict definition for a specific weight is given by Al-Khazini in The Book of the Balance of Wisdom:

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.

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

On the basis that there is denser air when nearer to the centre of the Earth (derived from the Archimedes principle), 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:

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, and the moment of a force relative to a point (both meanings were derived from al-Quhi and Alhacen). 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. 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, but in his second sense of the word, the concept was considered again by Jordanus de Nemore in the 13th century.

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

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.

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:

See also



  • 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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