Why Couldn’t Muslim Astronomers Discover the Heliocentric System?

Abstract

It comes to question the reasons why Muslim astronomers could not recognize the centrality of the Sun in the planetary system. While Europeans have spent centuries in their dark ages, Muslims spent the same centuries trying to verify the Ptolemaic planetary theory which has adopted the assumption of geocentricism, both theoretically and observationally. Many generations of Muslim astronomers from the 8th century to the 15th century lived circling in boring games of epicycles and deferments. Undoubtedly, Muslim astronomers devoted great efforts for developing the astronomical observations. For this purpose, they invented and developed many precise astronomical instruments and on the side of scientific literature, they wrote thousands of manuscripts in astronomy and observational techniques. This article questions the reasons why Muslim astronomers could not recognize the heliocentric system, despite their serious critique of the Ptolemaic geocentric model. For this purpose, we try to interrogate the astronomical manuscripts written by Muslim astronomers during the centuries before the Copernican breakthrough, since it is now believed that the efforts of Muslim astronomers have contributed great deal to the Copernican discovery of the heliocentric system. Some new studies in this area have already pointed to the fact that prominent Muslim astronomers have criticized the Ptolemaic geocentric system starting with the article of Ibn al-Haytham entitled “The Doubts about Ptolemy”, then al-Beruni’s assertion of the possibility of the spinning Erath while rotating around the Sun which comes in his assessment of the Indian astronomers' claim of the heliocentric model. The work of the astronomers of Muragha school and the Muragha observatory which was erected in 1259 and their models proposing to explain the observed planetary motions using the intelligent model of the “Tusi Couple”, in addition to the comments and suggestions of Ibn al-Shatir of Damascus about the lunar motion have contributed a great deal to the advancement of astronomy. These and many other flash points in the history of Islamic astronomy marked a strong zeal for a change that never took place. The question is: why could not Muslims adopt a new paradigm? This article emphasizes the fact that a transformation from the assumption of a geocentric system to a heliocentric system required a fundamental paradigm shift from the Aristotelian belief in the geocentric planetary system and the more developed Ptolemaic models. Such a paradigm was prevailing in the thoughts of Muslim philosophers as well as the religious clerics. We point to the fact that in addition to the observed reality of the celestial objects rotating around the Earth with different periods, the Aristotelian picture of the universe was in agreement with the interpretations of some verses of the Qur'an related to the celestial motion. We point here to the description of the heavenly spheres given by Ikhwan as-Safa who were a group of religious philosophers with some influence in the scientific circle. While being in doubt about the Ptolemaic models, Muslim astronomers were unable to continue their revolution to adopt a profoundly different model. The traditional understanding of some religious texts may have influenced the realization of some scientific facts. This may explain why Nasir al-Din al-Tusi, who belongs to the same sect of Ikwan as-Safa, resorted to device his couple to explain the apparently non-circular orbits of the planets by circular motion of his couple. However, we allude to the possibility that Muslim Mutakallimun could have achieved such a paradigm should they have the chance to continue their project on the Islamic worldview of nature. The endeavour of Mutakallimun to establish a rational and liberal attitude towards science and religion was negatively affected by their muddling with the theological question more than the questions related to natural philosophy. Internal fight between different factions of the Mutakallimun dispersed their efforts. Furthermore, the prohibition of kalam and the debates related to kalam aborted any progress in the rational approach to establish a scientific trend in religious studies. Keywords: Geocentric model, Heliocentric model, Ptolemy, Tusi couple, Islamic astronomy.