Newton paid tribute to his predecessors when he said that if he had seen farther than Descartes it was “by standing on the sholders of Giants.” The colossal figures he was referring to can be identified from his works, where he gives credit to his European predecessors, most notably Copernicus, Tycho Brahe, Kepler, and Galileo, and to the ancient Greeks, including Pythagoras, Empedo-cles, Philolaus, Democritus, Plato, Aristotle, Epicurus, Euclid, Archi medes, Apollonius, Aristarchus, Diophantus, Ptolemy, and Pappus of Alexandria.
But Newton makes no mention of any Arabic scientists, though surely he must have been aware that much of Greek science had been transmitted to Europe through the Islamic world. Islamic science effectively had come to an end by the time the Scientific Revolution began, and the works of medieval Arabic philosophers, physicists, mathematicians, astronomers, engineers, astrologers, and alchemists had been for the most part either lost or forgotten. The science of ancient Greece and medieval Islam had been supplanted by the new world system that had emerged during the Scientific Revolution, and that in the two centuries after Newton would give rise to the Industrial Revolution and the Atomic Age.
Historians of science until the mid-twentieth century were of the opinion that Islamic science reached its peak in the late medieval period and then declined rapidly, just as European science was beginning to emerge. William Cecil Dampier, whose History of Science and Its Relation with Philosophy and Religion appeared in three editions and twelve reprints between 1929 and 1945, devotes only 7 of the 574 pages of his book to Islamic science. He writes of the “absorption of Arabic knowledge by the Latin nations” beginning at the close of the eleventh century when, according the his view, “the decline of Arabic and Muslim learning had set in.”
The decline of Arabic science was accelerated by the rise of the Mongols and their sack of Baghdad in 1258 under Hulagu, who executed the last Abbasid caliph. This was a turning point in the history of eastern Islam, for the Mongol invasion opened up the way for the westward migration of Turkish-speaking people from the steppes of central Asia. The Seljuk Turks were followed by the Ottoman Turks, who after their conquest of Constantinople in 1453 created an empire that extended from southern Europe through the Middle East and North Africa. The Turkish historian Aydín Adívar, writing in 1939, put forward the view that the Ottoman sultanate cut itself off from Western science, which did not reach Turkey and the Middle East until after the collapse of the empire and the creation of the modern Republic of Turkey in 1923. But recent research has shown that Islamic science reached a new peak under the Mongols two centuries after their sack of Baghdad, and that it continued at a high level for at least another century under the Ottoman Turks before beginning its inexorable decline.
After the fall of the Abbasid dynasty several important astronomical observatories were founded in Central Asia by Mongol-Turkic rulers. The three most renowned were at Maragha and Tabriz, in Persia, and at Samarkand, in what is now Uzbekistan. A number of Arabic astronomers, physicists, and mathematicians made important advances at these observatories during the two centuries following the Mongol conquest of Baghdad, which has led at least one modern historian to describe that era as the golden age of Islamic science.
The Maragha observatory was founded in 1259 by the Ilkhanid Mongol ruler Hulagu Khan, grandson of Genghis Khan. The first director of the observatory and its research center, which included a school of astronomy and a library, was the Persian astronomer and mathematician Nasir al-Din al-Tusi (1201-74). The actual construction of the observatory and its instruments was directed by the astronomer Mu'ayyad al-Din al-‘Urdi (d. 1266) of Damascus.
Hulagu's deed of foundation gave the observatory financial independence, so that it survived his death in 1265 and continued in operation until 1316. During that time at least eighteen astronomers are known to have worked at Maragha, including one from North Africa and another from China. The instruments they used included a mural quadrant with a radius of more than sixty feet, graduated to read minutes of arc. These instruments were used by al-Tusi and his staff to compile the Zij-i Ilkhani, the Ilkhanid astronomical tables, which were completed in 1272 under Hulagu's successor, Abaqa Khan.
Al-Tusi also wrote a book for the general reader called The Treasury of Astronomy, which criticized Ptolemaic concepts such as the epicycle theory and introduced new planetary models. One of his innovations was the so-called al-Tusi couple, which has one circle rolling inside another to give a combination of two circular motions, a substitute for the Ptolemaic epicycles. The al-Tusi couple was used effectively by a number of his successors, both Arabic and European, up to and including Copernicus.
Besides his astronomical writings, al-Tusi, who was fluent in both Persian and Arabic, wrote numerous works on geometry, trigonometry, mineralogy, alchemy, astrology, philosophy, logic, ethics, and theology. His works on astronomy and mathematics were translated into Latin and were influential in the development of European science.
Mu'ayyad al-Din al-‘Urdi wrote a treatise devoted to the reform of Ptolemaic astronomy. Entitled simply A Book on Astronomy, it apparently predates al-Tusi's work on the same subject, and is thus the first Arabic work to offer an alternative to the Ptolemaic epicycle theory. One of his mathematical methods, known as Urdi's lemma, was also used by subsequent astronomers up to and including Copernicus.
Two other notable astronomers at the Maragha observatory were Muhyi al-Din al-Maghribi (d. ca. 1290) and Qutb al-Din al-Shirazi (1236-1311).
As his last name indicates, Muhyi al-Din was born in the Maghreb, Muslim northwest Africa. He first studied religious law in the Maghreb and then moved to Aleppo, where he served as court astrologer to the Ayyubid sultan al-Nasir II. By his own testimony, he escaped death when the Mongols conquered Syria by simply telling them that he was an astrologer. He then went to work with Nasir al-Din al-Tusi at the Maragha observatory where he remained for the rest of his days. His extant manuscripts include theCompendium of the Almagest and numerous other works in astronomy and mathematics, one of the latter being a commentary on the Conics of Apollonius.
Qutb al-Din al-Shirazi took his name from the Persian city of Shiraz, where his father, Mas'ud al-Qadharuni, was a renowned physician at the Muzaffari hospital. When Mas'ud died Qutb al-Din was only fourteen, but he was mature enough to take over his father's duties at the hospital, where he worked for the next ten years. He then went to Maragha to study astronomy and mathematics with Nasir al-Din al-Tusi, who later saw him as a rival and expelled him from the observatory. Al-Shirazi then went to Tabriz, where, under the patronage of the Ilkhanid Mongol ruler Ghazan Khan and his successor, Oljaytu, he founded an observatory that became the successor to the one at Maragha.
Al-Shirazi is credited with further developing the theory of the al-Tusi couple, which he had learned from al-Tusi at Maragha. His major astronomical work is The Limit of Understanding of the Knowledge of the Heavens, which, in addition to astronomy, has sections on mechanics, optics, meteorology, geography, geodesy, and cosmography. Another of his works is entitled A Book I Have Composed on Astronomy, but Do Not Blame Me Al-Shirazi is also renowned for his medical writings, particularly his commentary on the Canon of Ibn Sina, which he defended against the attacks of the theologians.
Al-Shirazi's most brilliant student at Tabriz was Kamal al-Din al-Farisi (1267-1319), whose last name is derived from his birthplace, the Persian city of Fars. At al-Shirazi's suggestion, al-Farisi wrote a series of commentaries on the optical works of Ibn al-Haytham, which he then followed with his own treatise on the science of light, entitled Revision of Optics
Al-Farisi made several advances on the researches of Ibn al-Haytham, most notably in his theory of the rainbow. Here he used a hollow glass sphere filled with water as an analogue for a raindrop. His studies led him to conclude that the rainbow is produced by a combination of refraction and internal reflection of sunlight in the individual drops of water suspended in the air after a rainfall. In the primary rainbow, according to his theory, the light enters the drop and is internally reflected once before leaving, undergoing refraction on entry and departure, while in the secondary bow there are two internal reflections. The colors are due to the refractions, with their order from red to blue inverted in the secondary bow due to the second internal reflection.
The Turkish historian Mustafa Nazif has concluded that al-Farisi published his theory of the rainbow at least a decade before Dietrich of Freiburg, whose researches on the same subject date to the years 1304-11 and led him to the same conclusion. Dietrich refers to the optical works of Ibn al-Haytham but he does not mention the writings of al-Farisi, which were never translated into Latin.
The observatory at Samarkand was founded in 1425 by the Timurid khan Ulugh Beg, grandson of the great Mongol ruler Tamerlane. The observatory was erected on the same site where Ulugh Beg had four years earlier built a madrasa, a college of theology to which he had added a school for advanced study in science and mathematics. He directed his foundation until 1449, when he was assassinated by his brother. Ulugh Beg's observatory closed a few years afterward, with a singular record of accomplishments despite its relatively brief lifetime.
The principal astronomer at the Samarkand observatory during its early years was Jamshid al-Kashi (d. 1429), from Kashan in northern Persia. Al-Kashi's principal astronomical work is the Zij-i Khaqani, a revision of the Zij-i Ilkhani of Nasr al-Din al-Tusi, to which he added trigonometric tables and descriptions of a number of different calendars that had been used in central Asia, including those of the Uigur Turks and the Ilkhanid Mongols. Another of his astronomical works, The Stairway of Heaven, is an attempt to measure the distance and sizes of the planets. Other treatises describe the astronomical instruments he used in his observations, some of them his own inventions.
Al-Kashi's best-known mathematical work is Miftah al-Hisab, an encyclopedia of elementary mathematics, used for centuries by astronomers as well as architects, surveyors, and merchants. He also wrote two other mathematical treatises in connection with his researches in astronomy, where his method of approximation in calculating precise trigonometric tables anticipates the work of later European mathematicians.
When al-Kashi died, in 1429, he was succeeded as chief astronomer by Qadi Zada al-Rumi (ca. 1364-ca. 1436). Qadi Zada was born and educated in Bursa, the first capital of the Ottoman Turks, in northwestern Asia Minor. He traveled to Samarkand and presented himself to Ulugh Beg, who in 1421 appointed him rector of his newly founded madrasa. After he became head of the observatory he wrote a number of treatises on astronomy and mathematics, including a commentary on the Almagest and a revision of Euclid's Elements
When Qadi Zada died (ca. 1436), he was succeeded as head astronomer by Ali al-Qushji (ca. 1402-1474). Ali was born in Samarkand, and took the name of Qushji, or Bird-Man, because in his youth he was Ulugh Beg's falconer. He subsequently served as Ulugh Beg's ambassador to China. After becoming chief astronomer he supervised the completion of Ulugh Beg's astronomical tables, the Zij-i Sultanai, published in 1438. These tables were probably first written in Persian and soon afterward translated into Arabic and Turkish.
Al-Qushji left Samarkand soon after Ulugh Beg's death. He later went to Istanbul as chief astronomer for the Ottoman sultan Mehmet II (r. 1451-81), known as Fatih, or the Conqueror, in honor of his capture of Constantinople in 1453. Al-Qushji's writings include two treatises dealing with the solution of Ptolemaic models, one for the moon and the other for Mercury, as well as an introductory work called The Fathiya Treatise on Astronomy, dedicated to Mehmet II.
The first observatory in Istanbul was founded during the reign of Sultan Murat III (r. 1574-95) by Takiyuddin al-Rashid (1526-1585), an astron omer from Damascus. Takiyuddin equipped the observatory with several new instruments of his own invention, as well as a mechanical clock that he had made himself. His first project at the observatory was to correct Ulugh Beg's astronomical tables. At least one of his measurements was more accurate than that of Tycho Brahe. This was the annual motion of the sun's apogee in the celestial sphere, which he measured as 63 seconds of arc and which Tycho recorded as 45, compared to the currently accepted value of 61.
Takiyuddin also made careful observations of the comet of 1578, though he does not appear to have drawn the same conclusion as Tycho Brahe, who said that the fiery body was passing through the planetary celestial spheres. The poet Aladdin al-Mansur, in his poem “Concerning the Appearance of a Fiery Stellar Body,” writes that the comet appeared on the first night of the holy month of Ramadan, “passing through the nine sections of the ephemeral world… / like a turban sash over the Ursa Minor stars.”
Takiyuddin's Istanbul Observatory.
Takiyuddin, who was also the court astrologer, saw the comet as a sign of good fortune and predicted that the Ottomans would gain victory in their war against the Persians. But the head of the Muslim religious hierarchy, the Sheikh ül-Islam Kadizade, convinced Sultan Murat that the observatory would bring disaster to the realm by prying into the secrets of nature, as evidenced by the fate of Ulugh Beg, who had been assassinated after his planetary tables were published, he argued. Aladdin al-Mansur writes of how the sultan questioned Takiyuddin: “People of learning have made inquiries concerning this. Oh you learned man of consciousness and perfection, inform me once more of the progress and the results of your observations. Have you entangled knots from the firmament in a hair-splitting manner?”
Takiyuddin answered, “In the Zij of Ulugh Beg there were many doubtful points, oh exalted king. Now through observations the tables have been corrected, and out of grief the heart of the foe has withered and twisted into coils. From now on, order the abolishment of the Observatory.”
Aladdin al-Mansur, in the last lines of his poem, describes the fate of the Istanbul observatory. “The King of Kings summoned the Head of the Halberdiers of his Bodyguard and gave him instructions for the demol-ishment and abolition of the Observatory. Orders were given that the Admiral should immediately rush to the Marine Ordnance Division and they should at once wreck the Observatory and pull it down from its apogee to its perigee.”
During the reign of Sultan Selim III (r. 1789-1807), efforts to modernize the Ottoman army led to the establishment, in 1793, of a school for artillery officers, originally called the Mühendishane-i Cedide, or Military Engineering School. The curriculum included classes on mathematics, geography, and astronomy, as evidenced by the lecture notes of Hüseyin Rifki Tamani, head teacher during the years 1806-17. But Tamani still based his astronomy teaching on the old Ptolemaic model, as he remarks at the conclusion of one lecture: “Let it be known that the universe in appearance is a sphere and its center is the Earth…. The Sun and Moon rotate around the globe and move about the signs of the zodiac.”
Ishak Efendi (1774-1836), who became head of the Mühendishane in 1830, wrote a four-volume survey of contemporary scientific knowledge in Europe, including the works of Descartes and Newton. The fourth volume included 257 pages on astronomy, in which he says that the Copernican theory can explain many astronomical events more easily than the old geocentric model of Ptolemy. The fourth volume of Ishak Efendi's work was first printed in 1834 in Istanbul; eleven years later it was reprinted in Cairo. During the last Ottoman century it was the principal source of knowledge in the empire for those interested in the new science that had been developed in western Europe.
The first attempt to establish an Ottoman institution of higher learning, the Darülfünun, in Turkish, was begun during the reign of Sultan Abdul Mecit (r. 1839-61), as part of the reform movement known as the Tanzimat. The Darülfünun, which registered its first students in 1869, was reorganized in 1900 on the model of American and European universities, including faculties of science and medicine. After the founding of the Republic of Turkey in 1923 the Darülfünun became the University of Istanbul and the old Mühendishane was reorganized as Istanbul Technical University.
Another scientific institution founded in the second half of the nineteenth century was the Rasathane-i Amiri, or Imperial Observatory, though its primary function was as a meteorological station. Turkish astronomers began making observations at the Rasathane in 1910, and soon after the establishment of the Republic of Turkey it was moved to its present site, at Kandilli on the Asian shore of the Bosphorus, also serving as a seismological research center as well as a weather station.
Today the Rasathane is attached to Bosphorus University (BU), established in 1971 in the buildings and grounds of the old Robert College (RC), which was founded as an American missionary school in 1863 on the European shore of the Bosphorus. I taught physics at RC-BU in the years 1960-76, and since 1993 I have been lecturing on astronomy and the history of science at BU, an institution that spans the gap between the Ottoman Empire and the Republic of Turkey, the old Turkey and the new.
One of the most important references in my history of science course these days is an encyclopedic work published in Istanbul in 2003 by Boris A. Rozenfeld and Ekmeleddin Ihsanoĝlu titled Mathematicians, Astronomers and Other Scholars of Islamic Civilisations and Their Works (7th–14th Centuries) Commonly known as MASI, the work is a survey of 1,711 scientists, whose manuscripts, along with 1,376 works whose authors are unknown, are preserved in the libraries of fifty countries. Most of the manuscripts are written in Arabic, but some are in Persian, Syriac, Sanskrit, Tajiki, Urdu, Old Turkish, Tatar, Uzbek, or other Asian languages. The subject headings under which the works are classified are mathematics, astronomy, mechanics, physics, music, mathematical geography, descriptive geography, chemistry and alchemy, mineralogy, meteorology, zoology, botany, philosophy and theology, literature and linguistics, and mysticism. The manuscript libraries listed in MASI include 29 in Iraq, 27 in Iran, 25 in Turkey, 15 in India, 10 in Egypt, 9 in Afghanistan, 8 each in Morocco and Russia, 6 each in Lebanon, Spain, and Syria, 5 each in Pakistan, Uzbekistan, and Yemen, 4 each in Tajikistan and Ukraine, 2 each in Algeria, Azerbaijan, Bosnia and Herzegovina, Portugal, Saudi Arabia, and Tunisia, and 1 each in Armenia, Bangladesh, Bulgaria, Georgia, Indonesia, Kazakhstan, Libya, Nigeria, Qatar, and Turkmenistan, to name only the countries that once had centers of Islamic science.
Sixteen of the manuscript libraries of Turkey listed in MASI are in Istanbul, including one at the Kandilli Rasathane, which is solely devoted to Ottoman astronomers. A number of my students in the history of science have written term papers on research they have done in the library at the Kandilli Rasathane, particularly on the observations of Takiyuddin, founder of the first observatory in Istanbul.
The richest collection of Islamic manuscripts in Istanbul is in the library of the Süleymaniye mosque complex, built in 1550-55 by Sultan Süleyman the Magnificent (r. 1520-66). The oldest of the manuscripts in the Süleymaniye library date back to the beginning of the Islamic renaissance in Baghdad. But since all of the manuscripts are either in Arabic, Old Turkish, or other languages indecipherable to me and my students, we are forced to rely on translations into modern Turkish or English, which has been done for only a very few works, or on scholarly surveys of Islamic science such as MAS!
The question my students always ask and try to answer is why Islamic astronomy declined so sharply after the time of Takiyuddin, whose contemporary Tycho Brahe paved the foundation for the new astronomy of western Europe. While trying to find an answer they are generally surprised to find that Islamic astronomers continued to scan the heavens long after the time of Takiyuddin. I tell them that it is because astronomy was one branch of science that was always accepted in Islam, since astronomers used their skills to determine the months of the Muslim calendar and the five times of daily prayer; to orient mosques toward the qibla, the direction of Mecca; to predict eclipses of the sun and moon; and to follow the motions of the planets so as to draw up horoscopes for the caliphs, khans, emirs, and sultans who employed them. Aladdin al-Mansur writes of how Takiyuddin saved his skin by interpreting the comet of 1578 as a most favorable omen for Sultan Murat III, although he was forced to sacrifice his observatory in the process.
And so Islamic astronomers continued to make observations in the same way as had their Arabic and Greek predecessors, while their European contemporaries began the intellectual revolution that led to the emergence of modern science. Thus the Islamic world was left behind as its vast empires declined and fell, living on the fading memory of the great accomplishments of its physicists, physicians, mathematicians, geographers, and astronomers, who passed on Greek science to the West along with the advances they had made on their own.