Was Muslim Astronomy the Harbinger of Copernicanism?

In De revolutionibus orbium celestium (On the Revolution of Heavenly Spheres) the Polish astronomer (Copernicus) mentions his ninth-century Muslim predecessor (al-Battani, 850-929) no fewer than 23 times. (Owen Gingerich)

The question: Was Muslim astronomy the harbinger of Copernicanism, does not seem to have a simple ‘yes’ or ‘no’ answer. The answer is probably both yes and no. If the essence of Copernicanism is viewed as heliocentric formulation, the answer then would be no because no evidence has come to light showing that Muslim astronomers leaned toward it. Many of them severely criticized Ptolemaic geocentric view but did not consider replacing it with the heliocentric concept. For example, “Haytham in the tenth-eleventh century wrote a scathing critique of Ptolemy’s work: ‘Ptolemy assumed an arrangement that cannot exist, and the fact that this arrangement produces in his imagination the motions that belong to the planets does not free him from the error he committed in his assumed arrangement, for the existing motions of the planets cannot be the result of an arrangement that is impossible to exist,’” Stanford Encyclopedia of Philosophy (Nicolaus Copernicus), http://setis.library.usyd.edu.au/stanford/entries/copernicus /index.html.

In the same vein, Ibn-e-Rushd asserted, “..the existence of an eccentric sphere or an epicyclic sphere is contrary to nature..The astronomy of our times offers no truth, but only agrees with the calculations and not with what exists,” (Owen Gingerich, Islamic Astronomy, Scientific American, April 1986). It was strange that even then the Muslim astronomers stuck to Ptolemaic astronomy and did not consider to test the heliocentric system instead.

The Muslim astronomers introduced many ingenious innovations in the Ptolemaic astronomy to make it practically workable. None of them, it appears, felt any compelling motivation to change over to heliocentrism because the answers that they sought could all be obtained from the geocentric system. For this purpose, they introduced several clever computational techniques, which could be, and were, used with the heliocentric planetary system also.

Helen Shaver in her review of Howard Turner’s book, Science in Medieval Islam, observed, “According to Turner, there are parallels to Copernicus’s work found within the work of Ibn-al-Shatir. He suggests that Copernicus, when visiting the Vatican library may have seen the fourteenth century manuscript that contained an illustration of al-Shatir’s concept of planetary motion.” Copernicus was in Italy from 1497 till 1503.

Note 4 of the item “Nicolaus Copernicus” included in Stanford Encyclopedia of Philosophy states, “In De revolutionibus he (Copernicus) uses the form of Tusi’s device with inclined axes for the inequality of the precession and the variation of the obliquity of the ecliptic, and in both the ‘Commentariolus’ and ‘De revolutionibus’ he uses it for the oscillation of the orbital planes in the latitude – theory… The planetary models for longitude in the ‘Commentariolus’ are all based upon the models of Ibn ash-Shatir – although the arrangement for the inferior planets is incorrect – while those for the superior planets in De revolutionibus use the same arrangement as Urdi’s and Shirazi’s model, and for the inferior planets the smaller epicycle is converted into an equivalent rotating eccentricity that constitutes a correct adaptation of Ibn ash-Shatir’s model. In both the Commentariolus and De revolutionibus the lunar model is identical to Ibn ash-Shatir’s…”

In as much as the mathematization of the planetary movement was concerned, the Musilm (Arab) contribution cannot be ignored particularly in view of the fact that they developed trigonometry, algebra, and spherical trigonometry, and this knowledge was fundamental to the astronomical computations. Only nominal acknowledgment of this fact is generally given in the traditional works on Copernicanism and other works on history of science. The Muslim contribution was indeed significant. The Muslim generations lost touch with the works of their ancestors during their scientific decline after 15th and 16th centuries. So much so that the original sources of knowledge determining the Muslim contributions, whatever they were (are), are mostly in the western countries. Although some work is being presently done by a few Muslim and Arab historians of science to examine the contributions of their ancestors, the Muslims, in general, and by and large, depend for this kind of knowledge primarily on the western sources. A number of western researchers and scholars are also currently engaged in determining the factual role that the Muslim/Arab astronomers played for ushering the Copernican revolution. According to Gingerich, “The .. impetus came from Islamic religious observances, mostly related to time keeping. In solving these problems the Islamic scholars went far beyond the Greek mathematical methods. These developments, notably in the field of trigonometry, provided the essential tools for the creation of the Western Renaissance astronomy… although the story of how Greek astronomy passed to the Arabs is comparatively well known, the history of its transformation by Islamic scholars and subsequent retransmission to the Latin West is only now being written.”

In view of the new developments in the field of astronomy and astrophysics after Kepler and Newton, the Copernican and pre-Copernican astronomy is almost eclipsed but when viewed in a historical perspective, the Muslim contributions were very significant in their own time. Even when the downfall of the Muslim civilization had set in after the fall of Baghdad to the Tartars, significant work in astronomy continued largely on the previous momentum. Nasir al Din Tusi who had attached himself with Halagu’s court after the fall of Alamut, persuaded Halagu to finance the construction of an observatory at Maragha. The observatory remained in operation for a couple of centuries and remarkable work was performed there. In addition to Tusi, two other astronomers at Maragha were quite prominent; they were Mu’ayyad-al-Din-al Urdi and Qutb-al-Din-al-Shirazi.

The Muslim astronomy was at the threshold of heliocentrism when the lead passed on to Europe. True motivation for Copernicus to adopt the heliocentric system is still a matter of debate because after taking this revolutionary step, he remained glued to Aristotelianism in other respects. There were three main points of the Aristotle astronomy, namely:

1. Earth is at the center of the universe and is stationary;
2. The planetary motion around Earth is uniform and unchanging and the orbits are circular in form; and
3. The heavenly bodies are flawless.

Copernicus believed religiously in the last two points. To keep the planetary motion uniform and circular, he stuck to the cumbersome systems of epicycles and epicycles-upon-epicycles borrowing the essentials of computational procedure from Tusi and Ibn-alShatir. Kepler did away with the circular orbits and made the heliocentric system simple and useful. Contrary to conventional belief, Copernican system was more cumbersome than the Ptolemaic system.

Deliberating on the question: Could Copernicus have been influenced by the Maragha astronomers or by Ibn-al-Shatir, Gingerich concluded that since “no Latin translation has been found of any of their works or indeed of any work describing their models,” it is unlikely. But because a lot of material remains still unexamined, it is not very improbable if such linkage came to light in the future.



Acknowledgment:
Samina Wahid Perozani suggested that I should consider writing on Copernican Revolution..I am pleased to acknowledge here the inspiration that I received from her suggestion.