Science in the medieval Islamic world
Science in the medieval Islamic world flourished across a vast territory for several centuries, producing breakthroughs in astronomy, medicine, mathematics, and optics that shaped the course of world knowledge. Between roughly 786 and 1258, under the Abbasid Caliphate of Baghdad and rulers stretching from Córdoba to Persia, scholars did not merely preserve the learning of ancient Greece and India. They argued with it, tested it, and in many cases overturned it.
Consider what was at stake. Ibn al-Haytham, working in the eleventh century, rejected ideas about vision held by both Aristotle and Euclid. Al-Razi, a physician born around 865, questioned Galen's theories that had guided medicine for centuries. Ibn Sina proposed a concept of inertia that would not be formally named until Jean Buridan described it as "impetus" roughly three centuries later. These were not passive translators. They were scientists in the full sense.
What made the Islamic world such a fertile ground for inquiry? Where did this science come from, and where did it go? And how did it reach the corners of medieval Europe, eventually feeding the Renaissance?
The Islamic era began in 622, and within decades Islamic armies had conquered Arabia, Egypt and Mesopotamia, displacing both the Persian and Byzantine Empires from the region. Within a century, Islam had stretched to the area of present-day Portugal in the west and Central Asia in the east.
This rapid expansion created something unusual: a vast, connected civilisation with a common language for scholarship. Major religious and cultural works were translated into Arabic, and occasionally Persian. Islamic culture absorbed Greek, Indic, Assyrian and Persian influences and wove them into a new common tradition. Trade and travel flourished. Cities grew rapidly alongside their populations.
From the 9th century onwards, scholars such as Al-Kindi translated Indian, Assyrian, Sasanian and Greek knowledge into Arabic, including the works of Aristotle. These translations did not simply preserve old ideas. They put old ideas into conversation with each other and with new observations from across the Islamic world, creating the conditions for genuine innovation. The Arab Agricultural Revolution, meanwhile, brought new crops and improved irrigation technology to the countryside, supporting the larger populations that sustained the cities where scholarship thrived.
The political centre of this era was the Abbasid Caliphate, founded in 750, with Baghdad established in 762. Stable governance and flourishing trade gave scholars the time and resources to work. Early in the Abbasid period, astronomers from India were invited to the court of the caliph. They explained the trigonometrical techniques used in Indian astronomy, techniques that would later be extended in directions their originators never imagined.
Al-Khwarizmi, working in the 8th to 9th centuries, was the first scholar to treat algebra as an independent discipline. He introduced methods for simplifying equations, used Euclidean geometry in his proofs, and presented the first systematic solutions to linear and quadratic equations. He was also instrumental in the adoption of the Hindu-Arabic numeral system, the counting system used throughout the world today.
The numeral system itself had its own journey. Sometime around the seventh century, Islamic scholars adopted the Hindu-Arabic system. A distinctive Western Arabic variant began to emerge around the 10th century in the Maghreb and Al-Andalus. These are the direct ancestors of the modern Arabic numerals on every keyboard and calculator.
Omar Khayyam, born in 1048 and known in the West primarily as a poet, calculated the length of the year to within five decimal places. He found geometric solutions to all thirteen forms of cubic equations and developed quadratic equations still in use. Ibn Ishaq al-Kindi, who lived from 801 to 873, worked on cryptography for the Abbasid Caliphate and gave the first known recorded explanation of cryptanalysis, including the first description of frequency analysis as a code-breaking method.
Jamshid al-Kashi, born around 1380, calculated pi correctly to seventeen significant figures. He is credited with several theorems of trigonometry including the law of cosines, also known as Al-Kashi's Theorem, and with a method resembling Horner's for calculating roots. Thabit ibn Qurra, who lived from 835 to 901, calculated the solution to a chessboard problem involving an exponential series. Islamic mathematics reached its highest point in the eastern part of the Islamic world between the tenth and twelfth centuries.
Islamic society paid careful attention to medicine, following a hadith enjoining the preservation of good health. Physicians inherited traditions from classical Greece, Rome, Syria, Persia and India, including the writings of Hippocrates on the four humours and the theories of Galen. What made Islamic physicians distinctive was their willingness to challenge these authorities through direct observation.
Al-Razi, born around 865, identified smallpox and measles as distinct conditions and recognised fever as part of the body's defenses rather than a sign of illness in itself. He wrote a 23-volume compendium drawing on Chinese, Indian, Persian, Syriac and Greek medicine. He questioned the classical Greek theory of how the four humours regulate life processes, and challenged Galen's treatment of bloodletting, arguing it was effective in ways different from what Galen had claimed.
Al-Zahrawi, who lived from 936 to 1013, was a surgeon whose 30-volume work al-Tasrif covered medical symptoms, treatments and pharmacology. Its final volume described surgical instruments, supplies and procedures that were pioneering for their time. Avicenna, born around 980, wrote The Canon of Medicine, the major medical textbook of the era.
Ibn al-Nafis, born in 1213, wrote a book on medicine influential enough to largely replace Avicenna's Canon in the Islamic world. One of his commentaries, discovered in 1924, described the circulation of blood through the lungs. That discovery preceded its independent formulation in Europe by several centuries. Islamic physicians, including Ibn Sina, also described clinical trials for determining the efficacy of drugs and substances.
Hunayn ibn Ishaq, who lived from 809 to 873, wrote Ten Treatises on the Eye, a work that remained influential in the West until the 17th century. Abbas ibn Firnas, born in 810, developed lenses for magnification and the improvement of vision. Ibn Sahl, working around the 940s to 1000s, discovered the law of refraction now known as Snell's law and used it to produce the first aspheric lenses that focused light without geometric aberrations.
Ibn al-Haytham, known in Latin as Alhazen and born in 965, fundamentally changed how people understood sight. He rejected two dominant Greek theories: the Aristotelian view that the form of a perceived object enters the eye, and the view of Euclid and Ptolemy that the eye emits a ray toward objects. In his Book of Optics, al-Haytham proposed that vision occurs because light rays form a cone with its vertex at the centre of the eye. He argued that light reflects from different surfaces in different directions, causing objects to appear as they do, and that the mathematics of reflection and refraction must be consistent with the anatomy of the eye itself.
Al-Haytham was also an early advocate of what we would now call the scientific method. He insisted that a hypothesis must be proved by experiments based on confirmable procedures or mathematical evidence. He held this position roughly five centuries before Renaissance scientists articulated similar principles. His Book of Optics stands as one of the most consequential scientific works to come out of the medieval period in any culture.
Abu Zayd al-Balkhi, who lived from 850 to 934, founded the Balkhi school of cartography in Baghdad and wrote an atlas called Figures of the Regions. Al-Biruni, born in 973, measured the radius of the Earth using a new method that involved observing the height of a mountain at Nandana, in what is now Pakistan. Al-Idrisi, born in 1100, drew a map of the world for Roger, the Norman King of Sicily, and also wrote the Tabula Rogeriana, a geographic study of the peoples, climates, resources and industries of the entire known world.
In astronomy, Al-Battani, who lived from 850 to 922, accurately determined the length of the solar year and contributed to the Tables of Toledo, used by astronomers to predict the movements of the sun, moon and planets. Copernicus, working between 1473 and 1543, later used some of Al-Battani's astronomical tables. Al-Zarqali, born in 1028, developed a more accurate astrolabe, constructed a water clock in Toledo, and discovered that the Sun's apogee moves slowly relative to the fixed stars.
Nasir al-Din al-Tusi, born in 1201, wrote an important revision to Ptolemy's second-century celestial model. When al-Tusi became Helagu's astrologer, he was given an observatory and gained access to Chinese techniques and observations. He developed trigonometry as a separate mathematical field. On the ground, botanist Al-Dinawari, who lived from 815 to 896, described 637 plants alphabetically in his Book of Plants, and detailed the phases of plant growth and the production of flowers and fruit. Only a portion of his original six-volume work survived, but the scope of what remains suggests the complete text described several thousand kinds of plants.
The sulfur-mercury theory of metals, which first appeared in the text known as The Secret of Creation and in writings attributed to Jabir ibn Hayyan, remained the basis of theories of metallic composition until the 18th century. The Emerald Tablet, a cryptic text that all later alchemists up to and including Isaac Newton regarded as the foundation of their art, also first occurs in The Secret of Creation and in one of the works attributed to Jabir. Jabir describes the synthesis of ammonium chloride from organic substances. Abu Bakr al-Razi, a Persian physician who lived from around 865 to 925, experimented with heating ammonium chloride, vitriol and other salts, work that would eventually lead to the discovery of the mineral acids by 13th-century Latin alchemists.
In pharmacology, Sabur Ibn Sahl, who died in 869, was the first physician to describe a large variety of drugs and remedies for ailments. Ibn al-Baytar, born in 1197, described a thousand simples and drugs based directly on Mediterranean plants collected along the entire coast between Syria and Spain, exceeding for the first time the coverage that Dioscorides had provided in classical times.
On the question of motion, Ibn Sina proposed that a moving object possesses a force that is dissipated by external agents like air resistance. He also claimed that a projectile in a vacuum would not stop unless acted upon. That idea accords with Newton's first law of motion on inertia, but it went essentially unrecognised as such until Jean Buridan described it as "impetus" around 1295 to 1363, likely influenced by Ibn Sina's Book of Healing. Abu'l-Barakat al-Baghdadi, working around 1080 to 1164, argued that velocity and acceleration are two different things and that force is proportional to acceleration rather than to velocity. The Banu Musa brothers, Jafar-Muhammad, Ahmad and al-Hasan, working in the early 9th century, invented automated devices described in their Book of Ingenious Devices.
Islamic science survived the initial Christian reconquest of Spain, including the fall of Seville in 1248, as work continued in eastern centres such as those in Persia. After the completion of the Spanish reconquest in 1492, the Islamic world entered an economic and cultural decline. The Abbasid Caliphate was followed by the Ottoman Empire, which ran from around 1299 to 1922 and was centred in Turkey, and the Safavid Empire, which lasted from 1501 to 1736 and was centred in Persia. Work in the arts and sciences continued under both.
Muslim scientists helped lay the foundations for experimental science through their contributions to the scientific method and their empirical, quantitative approach to inquiry. This science flourished for centuries across a wide range of institutions: observatories, libraries, madrasas, hospitals and courts. Its practitioners did not produce a Scientific Revolution in the mould of early modern Europe, but historians have argued that judging a successful medieval culture by such a standard imposes chronologically and culturally alien expectations.
What it did produce was knowledge that travelled. Copernicus used Al-Battani's tables. Newton read the Emerald Tablet. Ibn al-Nafis described pulmonary circulation in a commentary discovered only in 1924. The Ottoman admiral Piri Reis made a map of the New World and West Africa in 1513, drawing on sources from Greece, Portugal, Muslim cartographers, and perhaps a map made by Christopher Columbus himself.
Common questions
What was science in the medieval Islamic world?
Science in the medieval Islamic world refers to the scientific knowledge developed and practiced during the Islamic Golden Age, roughly between 786 and 1258, under dynasties including the Abbasid Caliphate of Baghdad, the Umayyads of Córdoba and rulers across Persia. It encompassed astronomy, mathematics, medicine, optics, chemistry, geography, botany and physics.
Who were the most important scientists of the Islamic Golden Age?
Key figures include Al-Khwarizmi, who founded algebra as an independent discipline; Ibn al-Haytham (Alhazen), who transformed the study of optics; Al-Razi, who identified smallpox and measles; Avicenna (Ibn Sina), who wrote The Canon of Medicine; Al-Biruni, who measured the Earth's radius; and Jamshid al-Kashi, who calculated pi to seventeen significant figures.
What mathematical contributions came from medieval Islamic scholars?
Islamic mathematicians developed algebra as an independent field, contributed to trigonometry, and were instrumental in adopting and transmitting the Hindu-Arabic numeral system that is used worldwide today. Al-Khwarizmi presented the first systematic solution of linear and quadratic equations, Omar Khayyam solved all thirteen forms of cubic equations geometrically, and Jamshid al-Kashi is credited with the law of cosines and calculated pi correctly to seventeen significant figures.
How did medieval Islamic science influence European science?
Copernicus used astronomical tables compiled by Al-Battani when developing his own work. The concept of inertia, which Ibn Sina articulated in his Book of Healing, was later described as "impetus" by Jean Buridan around 1295-1363. Works by pharmacologists such as Masawaih al-Mardini and Ibn al-Wafid were printed in Latin more than fifty times. Ibn al-Haytham's Book of Optics remained influential in the West for centuries.
What did Ibn al-Haytham discover about optics and vision?
Ibn al-Haytham (Alhazen), born in 965, rejected Greek theories of vision and proposed in his Book of Optics that vision occurs because light rays form a cone with its vertex at the centre of the eye. He argued that light reflects from surfaces in different directions, causing objects to appear as they do, and was an early advocate of the scientific method, insisting hypotheses must be proved by experiment or mathematical evidence.
When did medieval Islamic science decline?
Islamic science survived the initial Christian reconquest of Spain, including the fall of Seville in 1248. After the completion of the Spanish reconquest in 1492, the Islamic world entered an economic and cultural decline. Work in the arts and sciences continued under the subsequent Ottoman Empire (c. 1299-1922) and Safavid Empire (1501-1736).
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