جستجوی مقالات مرتبط با کلیدواژه « هیئت » در نشریات گروه « تاریخ »

Athīr al-Dīn Mufaḍḍal ibn ‘Umar Abharī, an astronomer, philosopher and mathematician (13th century) wrote many masterpieces in different domains as well as Hay’a or theoretical astronomy. There exists a manuscript including a set of there treatise under the title Thalāth Rasā’il. The first member of the set is Risāla fī al-Hay’a, an edition of which is presented here acconding to the only extant manuscript. This treatise could be categorise as an abridged hay’a book. The author presents a summary of theoretical Ptolemaic astronomy whithout argumentation. The text is followed by a commentary of the text and a biography of the author.

Mathematical geography is part of astronomical works in which is described the habited world, its division based on geographical latitudes and the way the sky appears in different latitudes. The last chapter of the Book I and the whole of the Book II of Almagest are devoted to mathematical geography based on mathematical computation and spherical geometry. In astronomical works of the Islamic period, in both Astronomical tables (Zījes) and cosmological works (Hayʾa books), one can find this subject in a separate part entitled “Hayʾa al-ʾArḍ”. The main difference between these two groups of texts is that Zījes are similar to Almagest whereas Hayʾa works are free from geometric demonstrations and examples. This paper investigates mathematical geography based on the first astronomical works in Islamic period written between 3rd to 5th centuries AH

Hayʾa works is a general name for the astronomical works which provide a geometrical description of the configuration of the world. Most of this kind of astronomical works were written by Islamic scholars probably under the influence of Ptolemy’s Planetary Hypotheses. Most of Islamic hayʾa works have a similar structure and order of chpters and have been written in 6AH/12AD century. Nevertheless, we have some astronomical works in 3-4AH/9-10AD centuries which have some similarities with the hayʾa works so that we can call them the “predecessors of hayʾa works”. Al-Farghānī’s Jawāmiʿ Ilm al-Nujūm and the third chpter of Kūshyār’s al-Zīj al-Jāmiʿ are two important works among these predecessors. Concidering the four chpter organization for Hayʾa works, i.e. mathematical and physical introduction, configuration of the heavens, mathematical geograpgy and masses and distances (Abʿād wa Ajrām), we compare in this article these two treatises with each other and other hayʾa works. This article claims that the third chapter of Kūshyār’s al-Zīj al-Jāmiʿ is more similar to the next Hayʾa works and probably it is more impressive.

Once the Greek astronomy's most worthy masterpiece, Ptolemy’s Almagest, was translated into Arabic, many scientific works were produced in Islamic civilization. The genre known as Hayʾa, which deals with the cosmological aspect of astronomy, gradually seperated itself from other astronomical branches. While these branches were in relation with each other, their goals were different. Computational astronomy, known as science of “Zijes”, was developed to produce arithmetical tables to forecast the position of the heavenly bodies in any given time. The science of astronomical instruments and science of timekeeping were two of the other branches of astronomy. Science of Haya uaully presents a non-technical descrpition of the large scale structure of the universe, i.e. the Earth and its position, configuration and size of the celestial spheres and the planets. In this article almost all of the Hayʾa books of Islamic civilization are listed and classified. Based on their manuscripts we mention their scientific specifications and compare them with each other. The golden age of these works in 12th century is studied in more details.

Physical explanation of the planets’ place in the heaven is one of the principal questions in the ancient astronomy which the authors of hay􁦦 a (cosmology) works tried to find an answer for it. Their opinion is in fact a compilation from Aristotle’s “fifth element” theory and Ptolemy’s “prisms” theory. Aristotle’s fifth element theory assumes that the substance of the heavens is different from the other four substances; i.e. Fire, Air, Water and Earth, and Aristotle named this substance fifth element. Moreover since emptiness doesn’t exist in the world it should be the fifth element that fills the heavens. This substance is the origin of the circular motion and its motion must be uniform but it doesn’t appear and the heavenly bodies have different motions in different periods. Because of this, we must accept the existence of several falaks (orbits) for the heavenly bodies. Ptolemy has discussed about the falaks place and their motions in his Planetary Hypotheses too. Muslim scientist’s attention to this subject in hay􁦦 a books shows their attempt to answer these questions. This article wants to survey the viewpoints of Aristotle, Ptolemy, Islamic philosophers and astronomers about the falaks of the heavenly bodies. Moreover we discuss the nature of the falaks and their motion in the heaven.