The Nizari Ismailis of the Alamut period: Astronomy

One thought

1. I strongly recommend all read Ragep’s 2007 paper at the link below:

   COPERNICUS AND HIS ISLAMIC PREDECESSORS:
   SOME HISTORICAL REMARKS
   http://digitool.library.mcgill.ca/R/?func=dbin-jump-full&object_id=108813&local_base=GEN01-MCG02

   Although not conclusive, yet, it is becoming clearer and clearer that Copernicus was heavily influenced by Muslim scientists, Tusi in particular. Indeed Copernicus used one of Tusi’s own diagrams unchanged in his own works (as can be seen in Ragep’s paper). The great “leap” Copernicus had — explained by him may not be so great, and may have already been there. Indeed there are records of Greeks having suggested the heliocentric solar system well before even the Muslims arrived on the scene.

   The issue for the Muslims was that Ptolemy’s model of the solar system did not match the observations and so the Muslims — who were at the peak of astronomy — had been working on the issue for 500 years on the issue and were closing in (if they hadn’t already) to solution. The revolutionary break through they had already made was realizing there was no need for the Earth to be stationary for their observations to still be valid. This was the real breakthrough as it went counter to 2,000 years of history and conditioning that the Earth was stationary. Once a moving Earth was allowed, a range of new possible solar system models became possible.

   Some extracts from Ragep’s paper:

   That Copernicus was acquainted with a number of his Islamic predecessors has
   been evident since 1543, when Copernicus in De revolutionibus explicitly cited five
   Islamic authors.1 The latest of these authors, al-Bitruji, flourished in Spain in the
   last part of the twelfth century, so Copernicus’s references end around 1200, which
   is the approximate terminus date for Islamic authors who were translated into Latin.
   Until recently, most historiography related to Copernicus has assumed that this was
   the end of the story, at least as far as Islamic influence goes. But since the 1950s, a
   series of discoveries has shaken this neatly constricted picture and caused a major
   re-evaluation of the relation of Copernicus (as well as other Renaissance astronomers)
   to later Islamic astronomy.

   The first modern acknowledgement of a connection between Copernicus and
   a later (i.e. post-1200) Islamic astronomer was made by J. L. E. Dreyer in 1906.
   In a footnote, Dreyer noted that the new device invented by Nasir al-Din al-Tusi
   (d. 1274) was also used by Copernicus in Book III, chap. 4 of De revolutionibus.2
   Typical for the time, Dreyer offered no further explanation or speculation; nor did
   anyone else until the discovery in the 1950s of a connection between another Islamic
   astronomer and Copernicus. E. S. Kennedy, who was a professor of mathematics
   at the American University of Beirut, happened by chance to notice some unusual
   (i.e. non-Ptolemaic) astronomical models while browsing through the Nihayat alsul
   of cAla’ al-Din Ibn al-Shatir, a Damascene astronomer of the fourteenth century
   who had been the time-keeper of the Umayyad Mosque. Upon showing these to his
   friend and mentor, Otto Neugebauer of Brown University, Kennedy was amazed to
   learn that these models were ones that had been thought to have first appeared in the
   works of Nicholas Copernicus. This led to a series of articles by Kennedy and his
   students that discussed various aspects of these models by Ibn al-Shatir as well as
   by other late Islamic astronomers.3 …

   THE CONNECTION TO COPERNICUS

   Noel Swerdlow and Otto Neugebauer, in discussing this Islamic tradition, famously
   asked: “What does all this have to do with Copernicus?” Their answer was: “Rather
   a lot.”13 In his commentary on Copernicus’s Commentariolus, Swerdlow made the
   case for this connection through a remarkable reconstruction of how Copernicus had
   arrived at the heliocentric system. According to Swerdlow, Copernicus, somehow
   aware of this Islamic tradition of non-Ptolemaic astronomy, began his work to reform
   astronomy under its influence. In particular Copernicus objected explicitly to Ptolemy’s
   use of the equant, an objection that had been a staple of Islamic astronomy for
   some five centuries at that point (but which seems not to have been made by earlier
   European astronomers).14 Swerdlow then proposed that although Copernicus was
   able to use some of these models, in particular those of Ibn al-Shatir, to deal with
   the irregular motion brought about by the first anomaly (the motion of the epicycle
   centre on the deferent), it was the second anomaly (related to the motion of the
   planet on the epicycle) that remained problematic. For the outer planets this motion
   corresponds to the motion of the Earth around the Sun, so a transformation of this
   motion from an epicyclic to an eccentric would lead to a quasi-heliocentric system,
   whereby the planet goes around the Sun. Of course the Earth could still remain at
   rest while the Sun, with the planets going around it, could then go around the Earth.
   In other words, Copernicus’s transformations could have led to a Tychonic system.
   Swerdlow argued that this was not an option for Copernicus, since it led to the notorious
   intersection of the spheres of the Sun and Mars, which simply was not possible
   in the solid-sphere astronomy to which Copernicus was committed. Thus Copernicus
   was compelled to opt for a heliocentric system with the Earth, as a planet, in motion
   around the Sun.15

   In his reconstruction, Swerdlow assumed that Copernicus must have had access
   to the models of his Islamic predecessors. Because of the scarcity of concrete evidence
   for this assertion (i.e. translated texts in Latin, earlier European references to these
   models, or the like), Swerdlow was clearly swayed by the similarity of complex
   geometrical models; independent discovery was simply not an option. As he stated
   with Neugebauer in 1984:

   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 cUrdi’s (sic) 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
   and finally in both works Copernicus makes it clear that he was addressing the
   same physical problems of Ptolemy’s models as his predecessors. It is obvious
   that with regard to these problems, his solutions were the same.
   The question therefore is not whether, but when, where, and in what form he
   learned of Maragha theory.16

   This has recently been reinforced by Swerdlow:

   How Copernicus learned of the models of his [Arabic] predecessors is not
   known — a transmission through Italy is the most likely path — but the relation
   between the models is so close that independent invention by Copernicus is all
   but impossible.17

   Neugebauer and Swerdlow did have one bit of evidence that seemed to show a
   likely means of transmission between the Islamic world and Italy. This was a text
   contained in MS Vat. Gr. 211, in which one finds the Tusi couple (rectilinear version)
   and Tusi’s lunar model. Apparently dating from about 1300, it is either a Greek
   translation or reworking of an Arabic treatise, made perhaps by the Byzantine scholar
   Gregory Chioniades.18 The fact that this manuscript found its way to the Vatican,
   perhaps in the fifteenth century, provides a possible means for the transmission of
   knowledge of Tusi’s models. It is also noteworthy that Tusi’s models seem to have
   been widely known by contemporaries of Copernicus; examples include Giovanni
   Battista Amico and Girolamo Fracastoro.19

   The historian of astronomy Willy Hartner also pointed to evidence for transmission
   from Islamic astronomers to Copernicus. Though he states that independent discovery
   of these models and devices by Copernicus was “possible”, “it seems more probable
   that the news of his Islamic predecessor’s model reached him in some way or other”.
   Here Hartner was speaking of the model of Ibn al-Shatir; he was more certain that
   another example “proves clearly” the borrowing by Copernicus of the Tusi couple
   inasmuch as the lettering in Copernicus’s diagram in De revolutionibus follows the
   standard Arabic lettering rather than what one might expect in Latin.20 …

   THE CONCEPTUAL BACKGROUND TO THE COPERNICAN REVOLUTION
   …
   Qushji was the son of the falconer of Ulugh Beg (1394–1449), the Timurid prince
   who was a generous patron of the sciences and arts. Ulugh Beg was an active supporter
   and participant in the magnificent Samarqand observatory, which was one of
   the greatest scientific institutions that had been established up to that time. As a boy,
   Qushji became his protégé and student and eventually occupied an important position
   at the observatory. After the assassination of Ulugh Beg, Qushji was attached to
   various courts in Iran but would end his career in Constantinople under the patronage
   of Mehmet II, who had conquered the city for the Ottomans.

   Qushji held that the astronomer had no need for Aristotelian physics and in fact
   should establish his own physical principles independently of the natural philosophers.
   39 This position had profound implications for one principle in particular, namely
   that the element earth had a principle of rectilinear inclination that precluded it from
   moving naturally with a circular motion.40 Tusi had maintained that there was no
   way for the astronomer, using mathematics and observation, to arrive at the “proof of
   the fact” that the Earth was either moving or at rest. This was contrary to Ptolemy’s
   position in the Almagest (I.7), namely that one could establish a static Earth through
   observation. After Tusi, we can trace a three-century discussion in which various
   authors argued whether he or Ptolemy was correct regarding the possibility of an
   observational proof of the Earth’s state of rest. Qushji, though, took a somewhat
   different approach. Starting with his view that the astronomer should not depend on
   the natural philosopher, but also rejecting Ptolemy’s view that an observational test
   was possible, Qushji made the remarkable claim that nothing false follows from the
   assumption of a rotating Earth.41

   The connection with Copernicus, though, might seem tenuous at best. What makes
   this an arguable possibility is the remarkable coincidence between a passage in De
   revolutionibus (I.8) and one in Tusi’s Tadhkira (II.1[6]) in which Copernicus follows
   Tusi’s objection to Ptolemy’s “proofs” of the Earth’s immobility.42 This passage,
   which is quoted by numerous Islamic scholars after Tusi, including Qushji, formed
   the starting point for their discussion of the Earth’s possible motion. The closeness
   of the passage in Copernicus is one more bit of evidence that he seems to have been
   influenced not only by Islamic astronomical models but also by a conceptual revolution
   that was going on in Islamic astronomy. This conceptual revolution was opening
   up the possibility for an alternative “astronomical” physics that was independent of
   Aristotelian physics.

   It is this point that has been missed up to now in seeking to understand the Islamic
   background to Copernicus. Clearly there is more to the Copernican revolution than
   some clever astronomical models that arose in the context of a criticism of Ptolemy.
   There also needed to be a new conceptualization of astronomy that could allow for an
   astronomically-based physics. But there is hardly anything like this in the European
   tradition before Copernicus.43 The fact that we can find a long, vigorous discussion
   in Islam of this issue intricately-tied to the question of the Earth’s movement should
   indicate that such a conceptual foundation was there for the borrowing. It will be
   argued, of course, that the mechanism for such borrowing has yet to be found. But
   again, in my opinion it is more important at this point in our knowledge to focus on
   the products rather than the mechanism of transmission. By doing so, we can get a
   clearer idea not only of the possible Islamic connection to Copernicus but also of
   the Copernican revolution itself.

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