But the same devices also embodied the application of very subtle principles that could awe masters and visitors alike. The historical sources report that those engineers had the ear of one of the caliphs of their time because they produced for him such vessels as pitchers that seemed full of liquid but nothing could be poured out of them or looked empty and yet could fill one cup after another. In it he states explicitly that he saw his function as describing devices that demonstrated how the hidden principles of nature worked, and with those devices he was only enabling principles that exist in potential to materialize in actuality.
From such language it becomes evident that his main interlocutor was the great Greek philosopher Aristotle who also was supposed to have devoted a short treatise to mechanical problems. But the idea that principles, or laws of nature, are always there in potential waiting to be revealed or actualized informed the basic assumptions of al-Jazari about the manner in which nature operated.
This meant that natural laws could be discovered, and illustrations of the manner in which they operated can be constructed. So in a sense all the devices that he described should be read as samples, as he explicitly says in the introduction to his work, of all types of machines that illustrate the same natural principles. Accordingly it becomes easy to understand why he tended to give several devices under each category as if trying to illustrate the same principle in so many different ways, and to say that nature's laws work in many different areas, and are not restricted to a specific set of circumstances to be revealed.
Of course, this theoretical rendering of the function of mechanical devices does not stop them from being very useful in real life. The clocks he described in his text could be very easily used for public exhibition of time as was indeed done according to the historical sources that described those clocks, or the archaeological remains of such clocks that have been preserved. Water fountains, water lifting devices, various types of drinking devices and locks could all be considered very useful for gardening, agriculture, diversion of rivers, and the like.
Similarly, drinking vessels, medical vessels that were used by physicians to measure the amount of blood extracted during blood-letting, or those vessels that assisted their owners with their ablution duties, all fulfilled very useful social functions. But the most awe-inspiring function those devices could fulfill was their deployment in political circumstances to impress upon a visiting ambassador the richness and awesome knowledge of the potentate, all in a political game of brinksmanship that is usually played among rulers.
For example, we are told by the historical sources that when an ambassador was sent to meet with the local potentate, he was taken to a room, which was decorated with an artificial tree with metallic birds attached to its branches.
History of science in the Renaissance
The birds began to chirp when the potentate sat down and stopped when he got up. Needless to say, the ambassador was highly impressed and obviously reported all that technological savvy back to his own country. The people who constructed those devices belonged to a class in Islamic society that is still poorly studied.
This class of artisans who produced the astrolabes, the large observational instruments, the celestial globes, the quadrants as well as the mechanical devices knew a lot about the behavior of materials, and about the crafting of exacting measures that allowed for precise observations, or rendered the solution of very sophisticated mathematical and astronomical problems easy to manipulate. They must have known the properties of alloys like brass, as well as the extent to which metal instruments could be enlarged before they began to collapse under their own weight.
The more sophisticated among them could have known about the mathematical principles governing the instruments they were constructing, like knowing the meaning of every curve they were to draw on an astrolabe, which required very sophisticated mathematical training. Those of them who produced a jewel-like map that was based on the projection that preserved the directions and distances to Mecca were obviously very competent astronomers and mathematicians at the same time. And those did not need much instruction as to how to perform their work. Some of them must have been employed in the various mint centers that produced the coins of the realm, while others must have also doubled as pharmacists or worked very closely with pharmacists on account of their knowledge of weights and measures.
The alchemical treatises that have survived c ontain linguistic expressions that are indicative of professional jargon that could have been employed by members of guild-like fraternities. And they were the ones who passed on their extensive knowledge of chemical processes like distillation to the Latin west through the translations of their alchemical treatises.
Common European words such as alcohol, alembic, etc, owe their origins to the works of such artisans. But there were others, who were manually skilled and did know, for example, how to engrave brass, but did not know much about the curves they were drawing. But when the armies of Halagu, the grandson of Genghis Khan, massed outside the city in , al-Tusi had little trouble deciding where his loyalties lay.
He joined Halagu and accompanied him to Baghdad, which fell in The grateful Halagu built him an observatory at Maragha, in what is now northwestern Iran. Al-Tusi's deftness and ideological flexibility in pursuit of the resources to do science paid off. The road to modern astronomy, scholars say, leads through the work that he and his followers performed at Maragha and Alamut in the 13th and 14th centuries. Commanded by the Koran to seek knowledge and read nature for signs of the Creator, and inspired by a treasure trove of ancient Greek learning, Muslims created a society that in the Middle Ages was the scientific center of the world.
The Arabic language was synonymous with learning and science for hundred years, a golden age that can count among its credits the precursors to modern universities, algebra, the names of the stars and even the notion of science as an empirical inquiry. Jamil Ragep, a professor of the history of science at the University of Oklahoma.
It was the infusion of this knowledge into Western Europe, historians say, that fueled the Renaissance and the scientific revolution. Abdelhamid Sabra, a retired professor of the history of Arabic science who taught at Harvard. Islam is a good example of that. But historians say they still know very little about this golden age.
Few of the major scientific works from that era have been translated from Arabic, and thousands of manuscripts have never even been read by modern scholars. Sabra characterizes the history of Islamic science as a field that ''hasn't even begun yet. Islam's rich intellectual history, scholars are at pains and seem saddened and embarrassed to point out, belies the image cast by recent world events. Traditionally, Islam has encouraged science and learning. So the notion that modern Islamic science is now considered ''abysmal,'' as Abdus Salam, the first Muslim to win a Nobel Prize in Physics, once put it, haunts Eastern scholars.
Bakar said. The relation between science and religion has generated much debate in the Islamic world, he and other scholars said. Some scientists and historians call for an ''Islamic science'' informed by spiritual values they say Western science ignores, but others argue that a religious conservatism in the East has dampened the skeptical spirit necessary for good science.
The Golden Age. When Muhammad's armies swept out from the Arabian peninsula in the seventh and eighth centuries, annexing territory from Spain to Persia, they also annexed the works of Plato, Aristotle, Democritus, Pythagoras, Archimedes, Hippocrates and other Greek thinkers.
Hellenistic culture had been spread eastward by the armies of Alexander the Great and by religious minorities, including various Christian sects, according to Dr. David Lindberg, a medieval science historian at the University of Wisconsin. The largely illiterate Muslim conquerors turned to the local intelligentsia to help them govern, Dr. Lindberg said. In the process, he said, they absorbed Greek learning that had yet to be transmitted to the West in a serious way, or even translated into Latin.
Among the first works rendered into Arabic was the Alexandrian astronomer Ptolemy's ''Great Work,'' which described a universe in which the Sun, Moon, planets and stars revolved around Earth; Al-Magest, as the work was known to Arabic scholars, became the basis for cosmology for the next years. Jews, Christians and Muslims all participated in this flowering of science, art, medicine and philosophy, which endured for at least years and spread from Spain to Persia. Al-Haytham, born in Iraq in , experimented with light and vision, laying the foundation for modern optics and for the notion that science should be based on experiment as well as on philosophical arguments.
The mathematician, astronomer and geographer al-Biruni, born in what is now part of Uzbekistan in , wrote some works totaling 13, pages, including a vast sociological and geographical study of India. Ibn Sina was a physician and philosopher born near Bukhara now in Uzbekistan in He compiled a million-word medical encyclopedia, the Canons of Medicine, that was used as a textbook in parts of the West until the 17th century.
Scholars say science found such favor in medieval Islam for several reasons. Part of the allure was mystical; it was another way to experience the unity of creation that was the central message of Islam. Knocking on Heaven's Door. Another reason is that Islam is one of the few religions in human history in which scientific procedures are necessary for religious ritual, Dr. Arabs had always been knowledgeable about the stars and used them to navigate the desert, but Islam raised the stakes for astronomy. The requirement that Muslims face in the direction of Mecca when they pray, for example, required knowledge of the size and shape of the Earth.
The best astronomical minds of the Muslim world tackled the job of producing tables or diagrams by which the qibla, or sacred directions, could be found from any point in the Islamic world. Their efforts rose to a precision far beyond the needs of the peasants who would use them, noted Dr.
Astronomers at the Samarkand observatory, which was founded about by the ruler Ulugh Beg, measured star positions to a fraction of a degree, said Dr. Islamic astronomy reached its zenith, at least from the Western perspective, in the 13th and 14th centuries, when al-Tusi and his successors pushed against the limits of the Ptolemaic world view that had ruled for a millennium. Names were given to these special groups of stars and the sky was divided into 28 regions, corresponding to the lunar month, where the moon was supposed to reside each night in one of those regions, called mansions, in its monthly path around the earth.
With the spread to the Islamic world of the Greek astronomical tradition during the eighth and the ninth centuries, Greek star lore began to compete with that of ancient Arabia in many circles of the newly emerging society. There were those who profited from translating the Greek astronomical tradition into Arabic and who could see that the mathematical character of that tradition allowed for a much higher precision in locating stars in the skies and thus allowed for much more developed techniques for computing the positions of the planets that seemed to wander amongst the stars.
The benefits derivable from such precision and calculations were way too tempting to ignore. And then there were others who saw the Islamic astronomical tradition as defined by a civilization that was first and foremost dependent on Arabic, the language of its holy text, and thus sought to revive the ancient Arabian traditions and systematize them in order to compete with the incoming "foreign" Greek tradition. This tense polarity between the two traditions, which was part of the tension that the imported Greek sciences and philosophy created as they were being assimilated by the newly-emerging Islamic tradition, became the hallmark of the literature that dealt with celestial imagery.
Neither school of thought was completely ascendant; both traditions survived next to each other, but in some sense to the detriment of the old Arabian tradition. It was the fame based on this work that earned al-Sufi the honor of a crater named for him, in the Latinized version of his name, Azophi, on the modern maps of the moon.
While combining the two traditions, he would give the description of each constellation, as he knew it from the Arabic translations of the Almagest , and then he would append to it the old Arabian lore concerning the various stars or groups of stars of that constellation.
In updating and recording the stars that were already observed by Ptolemy, he often would find himself in disagreement with the Greek text, either with respect to the longitude of the star, or its latitude, or even its magnitude. As a result, his book is dotted with such expressions as "both the longitude and the latitude are in error," as when he gave the new coordinates for the eighth star in the constellation of the Great Bear, or where a star was judged by Ptolemy to be of a particular magnitude, but al-Sufi found it to be of a different size and gave his own measurements, or when a star or group of stars was not even mentioned by Ptolemy.
In one instance, concerning the Andromeda Galaxy, al-Sufi was the first to notice the existence of the Andromeda Nebula. It thus remained unchallenged, not to be superseded until modern times. In a roundabout way, at least the nomenclature of the stars, which was used in the tabular part of the Persian translation of al-Sufi's text, was re-incarnated within the text of Ulugh Beg.
That text, in turn, was itself a subject of study by 17th-century English astronomers and was again reprinted in Washington, DC, towards the beginning of the 20th century. The migration of al-Sufi's text to Europe, and its widespread reception there, was brilliantly studied by Paul Kunitzsch in several articles published over the last 20 years or so. The intriguing questions raised by these quotations, especially given that we have no evidence that such Renaissance scientists knew any Arabic, highlight once more the urgent need to study the routes by which Islamic science managed to reach the learned scientific circles of Renaissance Europe.
Al-Qazwini's work was in turn translated into German towards the beginning of the 19th century, and through that translation many of the star names found their way to the modern star maps, such as one produced by the National Geographic Society in the s. The most important Greek astronomical work, Ptolemy's Almagest , was already more than years old when it was translated into Arabic, In Baghdad, during the early part of the ninth century.
The same work also contained the results of a host of observations that were either conducted by Ptolemy himself, or were reported by him on the authority of more ancient Greek and Babylonian sources.
Other Books By This Author
These two facts alone, and especially the passage of time, can easily explain why a small observational error, or a minute approximation either intentionally or unwittingly allowed by Ptolemy, would become many centuries later easily noticeable to ninth-century Baghdad astronomers. Thus, any mistake in the original Greek texts that could be noticed by a ninth-century observer would immediately threaten the validity of that text and could easily endanger other texts associated with it.
It would also threaten the persons who were importing and adopting those texts. Some of the errors were easy to notice, while others were subtler and required good scientific training to detect. In the first instance, prescribed mathematical operations in the original Greek texts could be easily double-checked and their results verified.
One such mistake, dealing with the length of the synodic lunar month, appeared to have been incorporated in the Greek text, and was silently corrected by the famous Arabic translator, al-Hajjaj Ibn Matar flourished circa Other equally important values could not be so easily corrected. For example, the measuring unit used in the Greek texts to calculate the size of the earth was systematically given in the usual Greek unit of stadion.
There were two very famous measurements in the Greek legacy: that of Ptolemy who gave the earth's circumference as being , stadions, and that of Eratosthenes, some four centuries before him, who gave the circumference as being , stadions.
The Scientific Revolution
So either there mist have been two types of stadion, or the measure of a stadion must have changed over time. For a ninth-century Baghdad astronomer, the measurements in this particular unit were confusing, and the stadion unit itself became essentially meaningless. It had to be "translated" into local units for there to be any hope of making sense of this data, a matter that was not so simple.
For how could one translate one system of units into another if one did not have a common reference measure for comparison? No such measure existed then, and the only recourse the Baghdad astronomers had was to measure the same physical object, in this case the length of one degree of the earth's circumference, in local units. The sources speak of a team of astronomers and mathematicians who were dispatched to the flat desert stretch in present-day northern Syria.
Renewal (Tajdid) in Islamic sciences
The team was supposed to split into two groups: one group to march north along a straight line and mark the ground when the height of the North Pole star increased by one degree, and the second group to march south, in the opposite direction, along the same line and mark the ground where the height of the Pole star decreased by one degree. Incidentally, everyone concerned knew that the height of the Pole star over a specific geographic locality was equal to the geographic latitude of that locality. The north and south distances were then measured in the local Arab miles of the time, and the results were averaged in order to increase their precision.
The value that emerged from this measurement was equivalent to The earth's circumference could then be calculated as the product of degrees and Other values, such as the rate of precession, the inclination of the ecliptic, and the position of the solar apogee were subjected to similar procedures of verification.
And in all instances, the traditional Greek values were found wanting. In the case of the precession of the fixed stars, that is the apparent dislocation of the fixed stars in respect to the point of the vernal equinox, the value that was determined by Ptolemy stipulated that the dislocation would be in the order of one degree every years. The positions of all those stars were measured with respect to the fixed point of the vernal equinox along the ecliptic circle, which is the middle circle of the zodiacal belt that marks the apparent yearly path of the sun.
One of the famous fixed stars, in the constellation of Leo, which was called Regulus, i. Measuring its position with respect to the vernal equinox was, therefore, relatively easy. According to Ptolemy's value for precession of one degree every years, this star should have been dislocated by seven degrees during the ninth century, that is, after years from the time when it was observed by Ptolemy.
But observers in ninth-century Baghdad, whose colleagues were measuring the size of the earth, also measured the position of Regulus and found it to have been dislocated by some 11 degrees instead of seven.
After repeating this measurement several times, they finally concluded that the Greek value of one degree every years was in fact too slow, and a better value to be adopted was one degree about every 70 years, a value much closer to the modern one. Similarly, the apparent yearly path of the earth around the sun gives rise to the various seasons that all the earth's inhabitants experience. The phenomenon of seasons is caused by the inclination of the earth's axis in relation to the plane described by the earth's path. According to the Greek tradition, the inclination of the earth's axis was determined by Ptolemy to be 23 degrees, 51 minutes, and 20 seconds.
And because ninth-century astronomers were in the process of double-checking these Greek values, they also tried to verify this inclination, the measurement of which is a relatively easy matter. It could also be highly precise if one used very large measuring instruments. The ninth-century Baghdad astronomers found the inclination to be around The difference between the Greek value and that determined in ninth-century Baghdad is close to 0. But when such small numbers were multiplied by the very large astronomical numbers that gave the term "astronomical" its frightening meaning, the results could become dramatically erroneous.