Suhayl. Journal for the History of the Exact and Natural Sciences in Islamic Civilisation

A Universal Sundial Made for Sultan Mehmet II, in the Context of Astronomical Instrumentation in late-15th Century Istanbul

2024-12-24T10:49:24+00:00

In this study we present a previously-unknown astronomical and mathematical instrument. This is a sundial for all latitudes made in 1477 and dedicated to the Ottoman Sultan Mehmet II who is known for his interest in astronomy. It is a unique example of a type of instrument previously known only from Arabic astronomical texts some two centuries earlier. This sundial, which enables the user to measure time from the solar altitude throughout the year, is conceived for all inhabited latitudes (as in classical geography, this would be from the equator to about 45°). By necessity, therefore, it is based on an approximate but practical formula for timekeeping.

In Islamic civilization sundials have a history of over 1,000 years, but this has yet to be documented on the basis of surviving sundials and texts – of these, universal sundials form a small but significant part. The immediate source of the design for this particular universal sundial can be identified as an Egyptian treatise on astronomical instruments from the late 13th century; however, the device itself was much earlier, maybe originating as far back as Baghdad ca. 900. The formula was known already to the earliest Muslim astronomer al-Fazārī in Baghdad ca. 750. This sundial is a mathematical device as well an astronomical one, in the sense that it was not really intended to be used as a practical time-telling device. It is so small that it would be difficult to measure time with it under any circumstances; the same is true of many hand-held astronomical instruments. It may be «universal» but one could hardly travel about with it. Nevertheless, at some time it was brought from Istanbul to Bucharest, either whilst the latter was still under Ottoman control or even thereafter. In fact, it is simply an intriguing object embodying mathematical quantities associated with an elegant astronomical formula for timekeeping, and a testimony to part of the essence of the transmission of ideas from Antiquity to the early Muslim world, thence to Mamluk Egypt and on to the early Ottoman world. And similar devices appear in Renaissance Europe. This «new» sundial reveals how little we knew previously about the astronomical interests of Mehmet II and their level of sophistication; it invites a new look at the relevant sources. This study deals with materials not yet incorporated into the current history of Ottoman astronomy. It casts light on astronomy and dialling in 15th-century Istanbul and it adds substantially to our knowledge of Mehmet II’s interest in astronomy.

Ptolemy and Jābir b. Aflaḥ on Solar Eclipses

2024-12-24T11:05:13+00:00

Abū Muḥammad Jābir b. Aflaḥ, a 12th-century Andalusian mathematician and astronomer, is recognized for his influential work al-Kitāb fī l-Hay ̓a, a work today better known as Iṣlāḥ al-Majisṭī. Jābir b. Aflaḥ’s al-Kitāb fī l-Hay ̓a is a reedition of Ptolemy’s Almagest in which he also included a number of criticisms of Ptolemy’s work. The present study focuses on Jābir b. Aflaḥ’s criticisms of Ptolemy’s theory of solar eclipses, highlighting three key objections: two on Ptolemy’s choice of the mid-heaven instead of the mid-heaven of the ascendant to obtain the parallax in longitude and its effect on solar eclipses; and an additional one on Ptolemy’s treatment of the lunar parallax in latitude. While two of these criticisms appear unjustified, they offer insight into Jābir’s methodology and his reliance on defective or abridged manuscripts. Jābir’s novel approach, particularly in his use of the new trigonometry, together with his disregard for certain celestial motions, reveal both his mathematical strength and his limitations in practical astronomy. His failure to account for the Sun’s additional motion in the computations of solar eclipses further underscores his inexperience. Nevertheless, Jābir b. Aflaḥ emerges as a creative astronomer, whose work demonstrates a deep engagement with and unfrequent understanding of Ptolemy’s Almagest, albeit with notable oversights in the practical aspects of astronomy.

On the Arabic Translations of Eutocius’ Commentary on Book II of Archimedes’ Sphere and Cylinder

2024-12-24T11:20:19+00:00

In the 9th century, parts of Eutocius’ commentary on Book II of Archimedes’ Sphere and Cylinder were translated into Arabic. Most extant manuscripts of these trans- lations contain only fragments. However, one manuscript, Escorial, Árabe 960, contains the longest known Arabic text of Eutocius’ commentary, at 41 folios long. Comparison with the Greek text reveals that the Arabic text in Escorial 960 is composed of the translations of two disjoint parts of Eutocius’ commentary, on Sphere and Cylinder II.1 and II.4. A comparison of various mathematical terms used in the two parts, which I call Text A and Text B, shows that they differ systematically, and were therefore probably translated by different individuals, in different scholarly contexts.

José Chabás (4.10.1948 – 9.6.2024)

2024-12-24T11:31:50+00:00

Ekmeleddin İhsanoğlu, The Ottoman Scientific Heritage. Vol. 1: The Formation, development and Issues, Al-Furqan Islamic Heritage Foundation, London, 2023.

2024-12-24T11:38:32+00:00

Ekmeleddin İhsanoğlu, The Ottoman Scientific Heritage. Vol. 1: The Formation, development and Issues, Al-Furqan Islamic Heritage Foundation, London, 2023, xxviii + 376 pp. Vol. 2, parts 1 and 2: The Compendium of Notable Scholars, Al-Furqan Islamic Heritage Foundation, London, 2023, xxxiv + 1586 pp.

Muḥammad Rawwās Qal ̔ah-jī and Muḥammad Ẓāfir Al-Wafā ̓ī (eds)., Amrāḍ al- ̔ayn wa-mu ̔ālajatuhā min kitābay al-Mu ̔ālajāt al-buqrāṭiyyah, allafahū Abū ’l-Ḥasan Aḥmad b. Muḥammad al-Ṭabarī t. ba ̔da 366 h. – 976 m.

2024-12-24T11:44:11+00:00

Muḥammad Rawwās Qal ̔ah-jī and Muḥammad Ẓāfir Al-Wafā ̓ī (eds)., Amrāḍ al- ̔ayn wa-mu ̔ālajatuhā min kitābay al-Mu ̔ālajāt al-buqrāṭiyyah, allafahū Abū ’l-Ḥasan Aḥmad b. Muḥammad al-Ṭabarī t. ba ̔da 366 h. – 976 m. wa-Firdaws al-ḥikmah allafahū ̔Alī b. Sahl Rabban al-Ṭabarī t. 247 h. – 861 m. Compiled, arranged, edited, and commented by Muḥammad Rawwās Qal ̔ah-jī and Muḥammad Ẓāfir al-Wafā ̓ī, London: Al- Furqān Islamic Heritage Foundation, Centre for the Study of Islamic Manuscripts, 1998, (368 pp). (Edited Texts Series 4).

Muḥammad Ẓāfir Al-Wafā ̓ī and Muḥammad Rawwās Qal ̔ahjī (eds)., Natījat al-fikar fī ̔ilāj amrāḍ al-baṣar. Ta ̓līf al-ra ̓īs Abū l- ̔Abbās Aḥmad b. ̔Uthmān b. Hibat Allāh al-Qaysī.

2024-12-24T11:47:42+00:00

Muḥammad Ẓāfir Al-Wafā ̓ī and Muḥammad Rawwās Qal ̔ahjī (eds)., Natījat al- fikar fī ̔ilāj amrāḍ al-baṣar. Ta ̓līf al-ra ̓īs Abū l- ̔Abbās Aḥmad b. ̔Uthmān b. Hibat Allāh al-Qaysī. Edited and commented by Muḥammad Ẓāfir al-Wafā ̓ī and Muḥammad Rawwās Qal ̔ah-jī, London: Al-Furqān Islamic Heritage Foundation, Centre for the Study of Islamic Manuscripts, 1998, (254 pp). (Edited Texts Series 5).

Ibrahim Ben Mrad (ed)., Kitāb al-I‛timād f al-adwiyah al-mufradah (The Reliable Book on Simple Drugs). By Abū Ja‛far Aḥmad Ibn Ibrāhīm Ibn Al-Jazzār (369 ah/979-980 ce).

2024-12-24T11:50:45+00:00

Ibrahim Ben Mrad (ed)., Kitāb al-I‛timād f al-adwiyah al-mufradah (The Reliable Book on Simple Drugs). By Abū Ja‛far Aḥmad Ibn Ibrāhīm Ibn Al-Jazzār (369 ah/979-980 ce). Edited by Ibrahim Ben Mrad, London: Al-Furqān Islamic Heritage Foundation, Centre for the Study of Islamic Manuscripts, 2019, (1090 pp). (Edited Texts Series).