Abū Ishaq Ibrahim al-Zarqali | |
|---|---|
.jpg) Fictional portrait by Eulogia Merle for theFundación Española para la Ciencia y la Tecnología (2011) | |
| Personal life | |
| Born | 1029 CE |
| Died | 1100 |
| Era | Islamic Golden Age |
| Region | Al-Andalus,Taifa of Toledo |
| Notable work(s) | Tables of Toledo |
| Religious life | |
| Religion | Islam |
Abū Isḥāq Ibrāhīm ibn Yaḥyā al-Naqqāsh al-Zarqālīal-Tujibi[2] (Arabic:إبراهيم بن يحيى الزرقالي); also known asAl-Zarkali orIbn Zarqala (1029–1100), was anArab maker of astronomical instruments and an astrologer from the western part of theIslamic world.[2]
Although his name is conventionally given as al-Zarqālī, it is probable that the correct form was al-Zarqālluh.[3] In Latin he was referred to asArzachel orArsechieles, a modified form ofArzachel, meaning 'the engraver'.[4] He lived inToledo,Al-Andalus before moving toCórdoba later in his life. His works inspired a generation ofIslamic astronomers in Al-Andalus, and later, after being translated, were very influential inEurope. His invention of theSaphaea (a perfected astrolabe) proved very popular and was widely used by navigators until the 16th century.[5]
The craterArzachel on theMoon is named after him.[4]
Al-Zarqālī, of Arab origin,[6][7][8] was born in a village near the outskirts ofToledo, the then capital of the newly establishedTaifa of Toledo. He started work after 1048 underSaid al-Andalusi for the EmirAl-Mamun of Toledo and also underAl-Mu'tamid of theTaifa of Seville. Assuming a leading position under Said, Al-Zarqālī conducted solar observations for 25 years from 1050.[9]
He was trained as ametalsmith and due to his skills he was nicknamedAl-Nekkach "the engraver of metals". His Latinized name, 'Arzachel' is formed from the Arabical-Zarqali al-Naqqash, meaning 'the engraver'.[4]
He was particularly talented ingeometry andastronomy. He is known to have taught and visitedCórdoba on various occasions, and his extensive experience and knowledge eventually made him the foremostastronomer of his time. Al-Zarqālī was also an inventor, and his works helped to putToledo on the intellectual center ofAl-Andalus. He is also referred to in the works ofChaucer, as 'Arsechieles'.[4]
In the year 1085, Toledo was taken by the Christian king of CastileAlfonso VI. Al-Zarqālī and his colleagues, such as Al-Waqqashi (1017–1095) had to flee. It is unknown whether the aged Al-Zarqālī fled toCordoba or died in aMoorish refugee camp.
His works influencedIbn Bajjah (Avempace),Ibn Tufail (Abubacer),Ibn Rushd (Averroës),Ibn al-Kammad,Ibn al-Haim al-Ishbili andNur ad-Din al-Betrugi (Alpetragius).
In the 12th century,Gerard of Cremona translated al-Zarqali's works into Latin. He referred to Al-Zarqali as an astronomer and magician.[4]Ragio Montanous[citation needed] wrote a book in the 15th century on the advantages of the Sahifah al-Zarqalia. In 1530, the German scholarJacob Ziegler wrote a commentary on one of al-Zarqali's works. In his "De Revolutionibus Orbium Coelestium", in the year 1530,Nicolaus Copernicus quotes the works of al-Zarqali andAl-Battani.[10]
Al-Zarqālī wrote two works on the construction of an instrument (anequatorium) for computing the position of the planets using diagrams of the Ptolemaic model. These works were translated into Spanish in the 13th century by order ofKing Alfonso X in a section of theLibros del Saber de Astronomia entitled the "Libros de las laminas de los vii planetas".
He also invented a perfected kind ofastrolabe known as "the tablet of al-Zarqālī" (al-ṣafīḥā al-zarqāliyya), which was famous in Europe under the nameSaphaea.[11][12]
There is a record of an al-Zarqālī who built awater clock, capable of determining the hours of the day and night and indicating the days of the lunar months.[13] According to a report found inal-Zuhrī'sKitāb al-Juʿrāfīyya, his name is given as Abū al-Qāsim bin ʿAbd al-Raḥmān, also known as al-Zarqālī, which has made some historians think that this is a different person.[3]
Al-Zarqali corrected geographical data fromPtolemy andAl-Khwarizmi. Specifically, he corrected Ptolemy's estimate of the width of theMediterranean Sea from 62 degrees to the correct value of 42 degrees.[10] In his treatise on the solar year, which survives only in a Hebrew translation, he was the first to demonstrate the motion of thesolar apogee relative to the fixed background of the stars. He measured its rate of motion as 12.04 arcseconds per year, which is remarkably close to the modern calculation of 11.77 arcseconds.[14] Al-Zarqālī's model for the motion of the Sun, in which the center of the Sun'sdeferent moved on a small, slowly rotating circle to reproduce the observed motion of the solar apogee, was discussed in the thirteenth century byBernard of Verdun[15] and in the fifteenth century byRegiomontanus andPeurbach. In the sixteenth centuryCopernicus employed this model, modified to heliocentric form, in hisDe Revolutionibus Orbium Coelestium.[16]
Al-Zarqālī also contributed to the famousTables of Toledo, an adaptation of earlier astronomical data byAl-Khwarizmi andAl-Battani, to locate the coordinates of Toledo.[9] Hiszij andalmanac were translated into Latin byGerard of Cremona in the 12th century, and contributed to the rebirth of a mathematically basedastronomy in Christian Europe and were later incorporated into theTables of Toledo in the 12th century and theAlfonsine tables in the 13th century.[17]
Famous as well for his ownBook of Tables, of which many had been compiled. Al-Zarqālī'salmanac contained tables which allowed one to find the days on which the Coptic, Roman, lunar, and Persian months begin, other tables which give the position of planets at any given time, and still others facilitating the prediction of solar and lunar eclipses.[18] This almanac that he compiled directly provided "the positions of the celestial bodies and need no further computation", it further simplifies longitudes using planetary cycles of each planet.[9] The work provided the true daily positions of the sun for fourJulian years from 1088 to 1092, the true positions of the five planets every 5 or 10 days over a period of 8 years forVenus, 79 years forMars, and so forth, as well as other related tables.[17][19]
In designing an instrument to deal with Ptolemy's complex model for the planetMercury, in which the center of thedeferent moves on a secondaryepicycle, al-Zarqālī noted that the path of the center of the primary epicycle is not a circle, as it is for the other planets. Instead it is approximatelyoval and similar to the shape of apignon (or pine nut).[20] Some writers have misinterpreted al-Zarqālī's description of an earth-centered oval path for the center of the planet's epicycle as an anticipation ofJohannes Kepler's sun-centeredelliptical paths for the planets.[21] Although this may be the first suggestion that aconic section could play a role in astronomy, al-Zarqālī did not apply the ellipse to astronomical theory and neither he nor his Iberian or Maghrebi contemporaries used an elliptical deferent in their astronomical calculations.[22]
Major works and publications:
It is, therefore, really al-Zarḳālī who must be credited with the invention of this new type of an astrolabe. Through theLibros del Saber (Vol. 3, Madrid 1864, 135-237:Libro de le acafeha) the instrument became known and famous under the nameSaphaea. It is practically identical withGemma Frisius'sAstrolabum ...
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