Message #146473

[Bianca]

                                                            Arabs and Astronomy






Written by Paul Lunde
and Zayn Bilkadi


The launch of Arabsat-B was Prince Sultan's primary assignment in space, but he also had to carry out, or participate in, four experiments and two of them - observation of the new moon and photography of the Arabian Peninsula - would not have been totally incomprehensible to medieval scientists in Islamic lands. They too were interested in such areas as optics, mapping and ephemerides - tables showing the positions of celestial bodies on given dates.


The observation of the new moon, for example, was, and is, important to Muslims; for religious purposes they follow a lunar calendar and the new moon marks the beginning and end of the fast of Ramadan and determines the date of the pilgrimage to Makkah (Mecca) - the Hajj - two of the five religious duties incumbent upon all Muslims.


Mapping too sprang from a religious concern: the need to establish correct coordinates of cities so that Muslims could determine the direction of Makkah - the qibla - towards which all Muslims prostrate themselves in prayer five times a day. And though observation of the new moon and determination of the qibla may seem prosaic subjects today, it was by pondering just such everyday phenomena that advances in science were made.


The mathematical determination of the qibla, for example, was no easy matter; in fact it was one of the most advanced problems in spherical astronomy faced by medieval astronomers and mathematicians. The trigonometric solution eventually found was of great sophistication, and trigonometry itself, largely an Arab development, is fundamental to the computation of planetary orbits as well as to terrestrial mapping. Nevertheless, medieval qibla tables often attained great accuracy. That of al-Khalili, who wrote in Syria in the 14th century, gives the coordinates of a large number of towns in degrees and minutes and is generally accurate to within one or two minutes. In Europe, this sort of accuracy in establishing geographical coordinates was not attained until much later.


It could be argued, in fact, that precise observation and an ability to find new mathematical solutions to old problems were the two main strengths of Muslim scientists in the Middle Ages. And though they, like their European counterparts, never fully escaped the tyranny of Aristotle and Ptolemy - whose models of terrestrial geography and of the heavens dominated men's minds until the Renaissance and were not finally demolished until the publication of Newton's Principia in 1687 - Muslim scientists were the first to express doubts about many of the details of the Ptolemaic system. Indeed, it was the growing awareness of the divide between Ptolemy's theoretical model of the universe and observed reality that culminated in the discoveries of Nicolaus Copernicus, Tycho Brahe and Johannes Kepler during the 15th to 17th centuries, and some of those doubts had been transmitted to European scientists from Spain in 12th- and 13th-century translations of Arabic scientific works.