The Birth of Science

Islam & Science

Astronomy in the Greek tradition was carried on in Islam, however. In just a century the followers of Muhammad (about 570 – 632) conquered all the Middle East to India, as well as North Africa and most of Spain. After their victories they became tolerant of diverse ideas and attitudes, and conditions for intellectual life improved in their domains. Starting around 750 and for the next 250 years, the caliphs of Baghdad became patrons of science and the city a center of learning. By the eleventh century the library of the caliph of Cairo contained roughly 150,000 volumes; by contrast, a Western monastery considered itself fortunate to have 150.

An important factor in the development of Islamic science was the old Greek writings that the Arabs found in the lands they conquered. Within just a few decades after 750 the major Greek scientific works were translated into Arabic; by the end of the tenth century essentially all the known Greek manuscripts had been translated. The atmosphere of tolerance was such that this work was done by Christians, Jews, and pagans, as well as by Islamic scholars.

The religious requirements of Islam were a powerful impetus to the study of astronomy. For example, Islam adopted (and generally still uses) a strictly lunar calendar, which, however, begins not at the time of the new Moon, but at the first sighting of the crescent Moon just after sunset. Calculating when this occurs requires fairly complex geometry. Since the lunar year is about 354 days long, the months of the Islamic year cycle through the seasons in about 33 years. Mosques had to be oriented toward Mecca, and Muslims were to pray facing in that direction. Furthermore, time-keeping was required to properly set the five times for daily prayer.

In attacking such problems, Islamic scholars developed mathematics, especially trigonometry and spherical geometry, far surpassing the Greeks. They learned of the sine trigonometric function from India, and invented the other five. They also derived some of the relations among these trigonometric functions, such as the law of sines. With these developments, it was far easier to solve the geometric problems of astronomy. The Arabs also used a system of numbers, including the concept of zero, which they had acquired from India, which in turn they transmitted to the West, and which we use today. These Arabic numerals, as they are called, are far easier to calculate with than are Roman numerals. Arab texts describing these new mathematical developments as well as various summaries and commentaries on the Almagest eventually found their way in Latin translation to the West, where they became standard works for centuries.

Islamic astronomers refined many of the basic astronomical constants, for example, the length of the year and the eccentricity and inclination of the Sun’s (really the earth’s) orbit, data that were later used in the West. Although they worked within the Ptolemaic tradition, they questioned some of the constructs of Ptolemy. The equant (the point around which the angular motion was uniform), for example, was felt not to conform to the requirement of uniform circular motion. Even epicycles were questioned, and attempts were made to construct a system that did not require them.

From our point of view, however, the Muslims’ most important contribution was that they preserved much of the Greek learning, and then, beginning around the year 1000, became the means by which it was retransmitted to the West. Cities near the boundaries between Islamic and Christian domains, such as Toledo in Spain, became centers of a “translation industry” (from Arabic to Latin) and Arabic words such as zenith, nadir, alchemy, algebra, and algorithm entered our language, along with star names such as Algol, Aldebaran, Alcor, Vega, Deneb, and Betelgeuse.

The richness, diversity, and power of the Greek writings made a deep impression on Western scholars, and soon they were attempting to accommodate them to the Christian tradition. Thomas Aquinas (1225 – 1274) was a key figure in this effort (called Scholasticism), and he showed how much of Aristotle’s thought could be integrated into Christianity. This amalgam became the foundation for natural science in the West.