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In the [[w:c:history:history of astronomy|history of astronomy]], '''Islamic astronomy''' or '''Arabic astronomy''' refers to the [[astronomical]] developments made in the [[Islamic world]], particularly during the [[Islamic Golden Age]] (8th-15th centuries),<ref>{{Harv|Saliba|1994b|pp=245, 250, 256–257}}</ref> and mostly written in the [[Arabic language]]. These developments mostly took place in the [[Middle East]], [[Central Asia]], [[Al-Andalus]], and [[North Africa]], and later in the [[Far East]] and [[History of India|India]]. It closely parallels the genesis of other [[Islamic science]]s in its assimilation of foreign material and the amalgamation of the disparate elements of that material to create a science with [[Islam]]ic characteristics. These included [[Iraqi astronomy|Sassanid/Mesopotamian]], [[Egyptian astronomy|Egyptian]]/[[Hellenistic astronomy|Hellenistic]] and [[wikipedia:Indian astronomy|Indian works]] in particular, which were translated and built upon.<ref name=Gingerich/> In turn, Islamic astronomy later had a significant influence on Indian,<ref>{{citation|first=Virendra Nath|last=Sharma|year=1995|title=Sawai Jai Singh and His Astronomy|publisher=Motilal Banarsidass Publ.|isbn=8120812565|pages=8–10}}</ref> [[Byzantine science|Byzantine]]<ref name=Leichter/> and [[Science in Medieval Western Europe|European]]<ref name=Saliba/> astronomy (see [[Latin translations of the 12th century]]) as well as [[Chinese astronomy]]<ref>{{citation|last=van Dalen|first=Benno|contribution=Islamic Astronomical Tables in China: The Sources for Huihui li|editor-last=Ansari|editor-first=S. M. Razaullah|year=2002|title=History of Oriental Astronomy|publisher=[[Springer Science+Business Media]]|isbn=1402006578|pages=19–32}}</ref> and [[Sankore Madrasah|Malian astronomy]].<ref>[http://books.google.com/books?id=4DJpDW6IAukC&pg=PA180&lpg=PA180&dq=astronomy+in+medieval+Africa&source=web&ots=wcw8-0WyuY&sig=kwrd2tUrfvMHNLFMSvFkdb-w44Y&hl=en&ei=V4yQSbaQLZaitgea1aSRCw&sa=X&oi=book_result&resnum=14&ct=result African Cultural Astronomy By Jarita C. Holbrook, R. Thebe Medupe, Johnson O. Urama]</ref><ref>[http://www.springerlink.com/content/p17743321v735124/ The Timbuktu Astronomy Project]</ref>
 
 
A significant number of [[star]]s in the [[sky]], such as [[Aldebaran]] and [[Altair]], and astronomical terms such as [[alhidade]], [[azimuth]], and [[almucantar]], are still today recognized with [[List of Arabic star names|their Arabic names]].<ref>{{cite web|url=http://www.icoproject.org/star.html|title=Arabic Star Names|date=2007-05-01|accessdate=2008-01-24|publisher=Islamic Crescents' Observation Project}}</ref> A large corpus of literature from Islamic astronomy remains today, numbering well over 10,000 Arabic manuscripts scattered throughout the world, most of which have not been read or catalogued. Thus, only an incomplete picture of Islamic astronomy can be reconstructed.<ref>{{Harv|Ilyas|1997}}</ref>
 
 
==Islam and astronomy==
 
{{See also|Islam and science|Islamic science}}
 
 
[[Islam]] has affected astronomy directly and indirectly. A major impetus for the flowering of astronomy in Islam came from religious observances, which presented an assortment of problems in mathematical astronomy, specifically in [[spherical geometry]].<ref name=Gingerich/>
 
 
===Background===
 
In the 7th century, both [[Christian]]s and [[Jew]]s observed holy days, such as [[Easter]] and [[Passover]], whos timing was determined by the [[phases of the moon]]. Both communities had confronted the fact that the approximately 29.5-day lunar months are not commensurable with the 365-day [[solar year]]. To solve the problem, Christians and Jews had adopted a scheme based on a discovery made in ''circa'' 430 BC by the [[Athenian]] astronomer [[Meton]]. In the 19-year [[Metonic cycle]], there were 12 years of 12 lunar months and seven years of 13 lunar months. The periodic insertion of a 13th month kept calendar dates in step with the seasons.<ref name=Gingerich/>
 
 
On the other hand, [[astronomer]]s used [[Ptolemy]]'s way to calculate the place of the [[moon]] and [[star]]s. The method Ptolemy used to solve [[spherical triangle]]s was a clumsy one devised late in the first century by [[Menelaus of Alexandria]]. It involved setting up two intersecting [[right triangle]]s; by applying [[Menelaus' theorem]] it was possible to solve one of the six sides, but only if the other five sides were known. To tell the time from the [[sun]]'s [[altitude]], for instance, repeated applications of Menelaus' theorem were required. For medieval Islamic astronomers, there was an obvious challenge to find a simpler [[trigonometric]] method.<ref name=Gingerich/>
 
 
===Islamic attitude towards astronomy===
 
{{See also|Islamic cosmology}}
 
 
Islam advised [[Muslim]]s to find ways of using the stars. The [[Qur'an]] says: "And it is He who ordained the stars for you that you may be guided thereby in the darkness of the land and the sea."<ref>{{cite quran|6|97|style=ref}}</ref> On the basis of this advice Muslims began to develop better observational and navigational instruments, thus most [[navigational stars]] today have Arabic names.<ref name=Gingerich/>
 
 
Other influences of the Qur'an on Islamic astronomy included its "insistence that the Universe is ruled by a single [[Physical law|set of laws]]" which was "rooted in the Islamic concept of ''[[Tawhid|tawhîd]]'', the unity of God", as well its "greater respect for [[empirical]] [[data]] than was common in the preceding Greek civilization" which inspired Muslims to place a greater emphasis on empirical [[observation]],<ref>{{citation|first=I. A.|last=Ahmad|title=The impact of the Qur'anic conception of astronomical phenomena on Islamic civilization|journal=Vistas in Astronomy|volume=39|issue=4|year=1995|pages=395–403|doi=10.1016/0083-6656(95)00033-X}}</ref> in contrast to ancient [[Greek philosophers]] such as the [[Platonists]] and [[Aristotelianism|Aristotelians]] who expressed a general distrust towards the [[sense]]s and instead viewed [[reason]] alone as being sufficient to understanding nature. The Qur'an's insistence on observation, reason and [[contemplation]] ("see", "think" and "contemplate"), on the other hand, led Muslims to develop an early [[scientific method]] based on these principles, particularly empirical observation. [[Muhammad Iqbal]] writes:<ref>{{citation|first=I. A.|last=Ahmad|contribution=The Rise and Fall of Islamic Science: The Calendar as a Case Study|title=Faith and Reason: Convergence and Complementarity|publisher=[[Al Akhawayn University]]|date=June 3, 2002|url=http://images.agustianwar.multiply.com/attachment/0/RxbYbQoKCr4AAD@kzFY1/IslamicCalendar-A-Case-Study.pdf |format=PDF|accessdate=2008-01-31}}</ref>
 
 
{{quote|“The general empirical attitude of the Qur'an which engendered in its followers a feeling of reverence for the actual, and ultimately made them the founders of modern science. It was a great point to awaken the empirical spirit in an age that renounced the visible as of no value in men's search after God.”}}
 
 
Several [[hadith]]s attributed to [[Muhammad]] also show that he was generally [[Muslim views on astrology|opposed to astrology]] as well as [[superstition]] in general. An example of this is when an [[eclipse]] occurred during his son [[Ibrahim ibn Muhammad]]'s death, and rumours began spreading about this being God's personal condolence. Muhammad is said to have replied:<ref>{{citation|first=James A.|last=Michene|title=Islam: The Misunderstood Religion|journal=[[Reader's Digest]]|date=May 1955|pages=68–70}}</ref>
 
 
<blockquote>"An eclipse is a phenomenon of nature. It is foolish to attribute such things to the death or birth of a human being."</blockquote>
 
 
From the 12th century onwards, Islamic astronomy began becoming a science primarily dependant upon observation rather than philosophy, primarily due to religious opposition from [[Islamic theology|Islamic theologians]] of the [[Ash'ari]] school, most prominently [[Al-Ghazali]], who opposed the interference of [[Aristotelian physics]] and [[On the Heavens|Aristotelian cosmology]] in astronomy, opening up possibilities for an astronomy unrestrained by [[Aristotelianism|Aristotelian]] philosophy.<ref name=Ragep/><ref name=Ragep2/> For example, the Ash'ari doctrine influenced the theologian [[Fakhr al-Din al-Razi]] (1149–1209) to reject the Aristotelian notion of the [[Geocentric model|Earth's centrality]] within the [[universe]] and instead propose the notion of a [[multiverse]] consisting of countless [[world]]s and universes, "such that each one of those worlds be bigger and more massive than this world as well as having the like of what this world has." Al-Razi also criticized the Aristotelian notion of solid [[celestial spheres]] and suggested these may be "merely the abstract orbit traced by the stars."<ref name=Setia/> The theologian Adud al-Din al-Iji (1281–1355), under the influence of the Ash'ari doctrine of [[occasionalism]], rejected many [[On the Heavens|Aristotelian cosmological]] theories that he insisted were purely conjectural and hypothetical, including the Aristotelian and [[Geocentric model#Ptolemaic system|Ptolemaic]] principle of [[uniform circular motion]] in the heavenly bodies,<ref name=Huff-175>{{Harv|Huff|2003|p=175}}</ref> and maintained that the celestial spheres were "imaginary things" that did not physically exist.<ref name=Ragep2/> Under such influences, [[Ali Kuşçu|Ali al-Qushji]] (d. 1474) rejected Aristotelian physics and completely separated it from astronomy, allowing astronomy to become a purely [[empirical]] and mathematical science. This allowed him to explore alternatives to the Aristotelian notion of a stationery Earth, as he explored the idea of a [[Earth's rotation|moving Earth]]. He concluded, on the basis of empirical evidence rather than speculative philosophy, that the moving Earth theory is just as likely to be true as the stationary Earth theory and that it is not possible to empirically deduce which theory is true (see ''[[#Astronomical physics and Earth's motion|Astronomical physics and Earth's motion]]'' section below).<ref name=Ragep/><ref name=Ragep2/>
 
 
===Islamic rules===
 
{{See also|Sharia|Fiqh|Islamic calendar|Qibla|Salah}}
 
There are several rules in Islam which lead Muslims to use better astronomical calculations and [[observation]]s.
 
 
The first issue is the [[Islamic calendar]]. The [[Qur'an]] says: "The number of months in the sight of Allah is twelve (in a year) so ordained by Him the day He created the heavens and the earth; of them four are sacred; that is the straight usage."<ref name=Gingerich/><ref>{{cite quran|9|36|style=ref}}</ref> Therefore Muslims could not follow the [[Liturgical year|Christian]] or [[Hebrew calendar]]s and they thus had to develop a new one.
 
 
The other issue is moon sighting. Islamic months do not begin at the astronomical [[new moon]], defined as the time when the moon has the same [[celestial longitude]] as the sun and is therefore invisible; instead they begin when the thin [[crescent moon]] is first sighted in the western evening sky.<ref name=Gingerich/> The Qur'an says: "They ask you about the waxing and waning phases of the crescent moons, say they are to mark fixed times for mankind and [[Hajj]]."<ref>{{cite quran|2|189|style=ref}}</ref><ref>{{citation|url=http://www.almizan.org/Tafseer/Volume3/Baqarah47.asp|chapter=Volume 3: Surah Baqarah, Verse 189|author=Syed Mohammad Hussain Tabatabai|title=Tafsir al-Mizan|accessdate=2008-01-24}}</ref>
 
This led Muslims to find the phases of the moon in the sky, and their efforts led to new mathematical calculations and observational instruments, as well as a special science being formed specifically for moon sighting.<ref>{{cite web|url=http://www.chowk.com/site/articles/index.php?id=4026|title=The Science of Moon Sighting|author=Khalid Shaukat|date= September 23, 1997|accessdate=2008-01-24}}</ref>
 
 
Muslims are also expected to pray towards the [[Kaaba]] in [[Mecca]] and orient their [[mosque]]s in that direction. Thus they need to determine the direction of Mecca from a given location.<ref>{{cite quran|2|144|style=ref}}</ref><ref>{{cite quran|2|150|style=ref}}</ref> Another influencing factor is the [[Salat times|time of Salah]]. Muslims need to determine from [[celestial bodies]] the proper times for the prayers at [[sunrise]], at [[Noon|midday]], in the [[afternoon]], at [[sunset]], and in the [[evening]].<ref name=Gingerich/><ref name=Tabatabai>{{citation|url=http://www.almizan.org/Tafseer/Volume2/Baqarah32.asp|author=Syed Mohammad Hussain Tabatabai|work=Tafsir al-Mizan|chapter=Volume 2: Surah Baqarah, Verses 142-151|accessdate=2008-01-24}}</ref>
 
 
===Necessity of spherical geometry===
 
{{See also|Islamic mathematics}}
 
 
Predicting just when the crescent moon would become visible is a special challenge to Islamic mathematical astronomers. Although [[Ptolemy]]'s theory of the complex lunar motion was tolerably accurate near the time of the new moon, it specified the moon's path only with respect to the [[ecliptic]]. To predict the first visibility of the moon, it was necessary to describe its motion with respect to the [[horizon]], and this problem demands a more sophisticated [[spherical geometry]].<ref>''The history of the telescope'' Henry C. King, Harold Spencer Jones, Courier Dover Publications, 2003 ISBN 0486432653, 9780486432656</ref> Finding the direction of [[Mecca]] and the time of [[Salah]] are the reasons which led to Muslims making advances in spherical geometry. Solving any of these problems involves finding the unknown sides or angles of a triangle on the [[celestial sphere]] from the known sides and angles. A way of finding the time of day, for example, is to construct a triangle whose [[Vertex (geometry)|vertices]] are the [[zenith]], the north [[celestial pole]], and the sun's position. The observer must know the altitude of the sun and that of the pole; the former can be observed, and the latter is equal to the observer's [[latitude]]. The time is then given by the angle at the intersection of the [[Meridian (astronomy)|meridian]] (the [[Arc (geometry)|arc]] through the zenith and the pole) and the sun's [[hour circle]] (the arc through the sun and the pole).<ref name=Gingerich/><ref name=Tabatabai/>
 
 
===Cosmological interpretations===
 
{{main|Islamic cosmology}}
 
 
There are several verses in the [[Qur'an]] (610-632) which some medieval and modern writers have interpreted as foreshadowing modern [[Cosmology|cosmological]] theories.<ref name=Salem>{{citation|title=The Evolution of the Universe: A New Vision|author=Kamel Ben Salem|journal=European Journal of Science and Theology|year=2007|url=http://www.akamaiuniversity.us/pdf/BenSalem_JAHC_051.pdf|accessdate=2010-03-19}}</ref> An early example of this can be seen in the work of the Islamic theologian [[Fakhr al-Din al-Razi]] (1149–1209), in dealing with his [[Physics in medieval Islam|conception of physics]] and the physical world in his ''Matalib''. He discusses Islamic cosmology, criticizes the idea of the [[geocentric model|Earth's centrality]] within the universe, and explores "the notion of the existence of a [[multiverse]] in the context of his commentary" on the Qur'anic verse, "All praise belongs to God, Lord of the Worlds." He raises the question of whether the term "worlds" in this verse refers to "multiple [[world]]s within this single [[universe]] or [[cosmos]], or to many other universes or a multiverse beyond this known universe." He rejects the Aristotelian view of a single world or universe in favour of the existence of multiple worlds and universes, a view that he believed to be supported by the Qur'an and by the [[Ash'ari]] theory of [[atomism]].<ref name=Setia/>
 
 
In modern times, the following verses in the Qur'an have been interpreted as foreshadowing the [[Metric expansion of space|expansion of the universe]] and possibly even the [[Big Bang]] theory:<ref>{{cite web|author=A. Abd-Allah|url=http://www.usc.edu/dept/MSA/quran/scislam.html|title=The Qur'an, Knowledge, and Science|publisher=[[University of Southern California]]|accessdate=2008-01-22}}</ref>
 
 
<blockquote>Don't those who reject faith see that the heavens and the earth were a single entity then We ripped them apart?<ref>{{cite quran|21|30|style=ref}}</ref></blockquote>
 
<blockquote>And the heavens We did create with Our Hands, and We do cause it to expand.{{cite quran|51|47|style=ref}}</blockquote>
 
 
Others have interpreted the following verse as foreshadowing the modern concept that the [[figure of the Earth]] has an [[Earth ellipsoid|ellipsoid shape]]:<ref name=Salem/>
 
 
<blockquote>"After that (God) spread the Earth out (''dahaha: from the verb 'daha''')."<ref>{{cite quran|79|30|style=ref}}</ref></blockquote>
 
 
The interpretation of this as implying an ellipsoid shape is explained by Kamel Ben Salem:
 
 
{{quote|Because they did not understand the meaning of this verse, (since they did not imagine that the [[Spherical Earth|Earth was spherical]]) the ancient exegetes had earlier explained the Arabic verb (dahaha) by (has flattened it). The same explanation has been introduced in the Arab dictionaries. But in these very dictionaries, the origin of this verb is found in the word (Ud-hiya), which means, "[[Ostrich Egg|egg of ostrich]]". Thus the Earth would look like an ostrich’s egg. The same verb is also used to refer to the action of rain on the pebbles, which the water current moves.<ref name=Salem/>}}
 
 
As such, [[Rashad Khalifa]] alternatively translated the verse as:
 
 
{{quote|He made the earth egg-shaped.<ref>{{citation|title=Quran: the final testament|author=Rashad Khalifa|year=2001|isbn=1881893057|page=497}}</ref>}}
 
 
==History==
 
[[Pre-Islamic Arabia]]n knowledge of [[star]]s was [[empirical]]; their knowledge was what they observed regarding the rising and setting of stars. The rise of [[Islam]] is claimed to have provoked increased [[Arab]] thought in this field.<ref name=Dallal162>{{Harv|Dallal|1999|p=162}}</ref> The foundations of Islamic astronomy closely parallels the genesis of other Islamic sciences in its assimilation of foreign material and the amalgamation of the disparate elements of that material to create a science that was essentially Islamic. These include [[Indian astronomy|Indian]], [[Sassanid Empire|Sassanid]] and [[Hellenistic civilization|Hellenistic]] works which were [[translation|translated]] and built upon.
 
 
The science historian [[Donald Routledge Hill]] has divided the history of Islamic astronomy into the four following distinct time periods in its history:<ref name=Dallal162/>
 
*Assimilation and syncretization of earlier Hellenistic, Indian and Sassanid astronomy (700&mdash;825 [[Anno Domini|AD]])
 
*Vigorous investigation, and acceptance and modification to the [[Ptolemaic system]] (825&mdash;1025 [[Anno Domini|AD]])
 
*Flourishing of a distinctive Islamic system of astronomy (1025&mdash;1450 [[Anno Domini|AD]])
 
*Stagnation, where few significant contributions were made (1450&mdash;1900 [[Anno Domini|AD]])
 
 
===610-700===
 
From the beginning, Muslim community in Medina sight [[new moon]] to determine the lunar months especially Ramadan and holy days.
 
 
In approximately 638 A.D, [[Caliph]] [[Umar]] introduced a new lunar calendar which is known as [[lunar calendar]] was made on the basis of Islamic view point. This calendar has twelve lunar months, the beginnings of which are determined by the sighting of the crescent moon. This calendar is about 11 days shorter than the solar year. This calendar is still in use for religious purposes among Muslims.<ref name=Gingerich/><ref>[http://islam.about.com/cs/calendar/a/hijrah_calendar.htm What is the Hijrah Calendar?]</ref>
 
 
===700-825===
 
This period was most notably the period of assimilation and syncretization of earlier Hellenistic, Indian and Sassanid astronomy occurred during the eighth and early ninth centuries.
 
 
====Impetus====
 
Historians point out several factors that fostered the growth of Islamic astronomy. The first was the proximity of the [[Muslim world]] to the world of ancient learning. Much of the ancient [[Greek language|Greek]], [[Sanskrit]] and [[Middle Persian]] texts were translated into [[Arabic]] during the ninth century. This process was enhanced by the tolerance towards scholars of other religions.<ref name=Gingerich>{{Harv|Gingerich|1986}}</ref>
 
 
Another impetus came from Islamic religious observances, which presented a host of problems in mathematical astronomy. In solving these religious problems the Islamic scholars went far beyond the Greek mathematical methods.<ref name=Gingerich/>
 
 
====Ancient influences and translation movement====
 
During this period, a number of [[Sanskrit]] and [[Middle Persian]] texts were first translated into [[Arabic language|Arabic]]. The most notable of the texts was ''[[Zij|Zij al-Sindhind]]'',<ref>This book is not related to al-Khwarizmi's ''Zij al-Sindh''. On ''zijes'', see {{Harv|Kennedy|1956}}</ref> based on the ''[[Surya Siddhanta]]'' and the works of [[Brahmagupta]], and translated by [[Muhammad al-Fazari]] and [[Yaqūb ibn Tāriq]] in 777. Sources indicate that the text was translated after an [[Indian astronomy|Indian astronomer]] visited the court of [[Caliph]] [[Al-Mansur]] in 770. The most notable Middle Persian text translated was the ''Zij al-Shah'', a collection of astronomical tables compiled in Sassanid Persia over two centuries.
 
 
One of the earliest original works in Islamic astronomy was by Yaqūb ibn Tāriq, who was mainly influenced by the Indian tradition. He estimated the distances of all the celestial bodies from the Earth and their diameters in a table. For example, his estimate for the distance between the Earth and the Sun was 8,000 times the [[Earth radius]], which was the largest known estimate for the [[astronomical unit]] up until that time.<ref>{{citation|title=Alberuni's India: An Account of the Religion, Philosophy, Literature, Geography, Chronology, Astronomy, Customs, Laws and Astrology of India|author=[[Abu Rayhan Biruni|Biruni Muhammad Ibn Ahmad]]|publisher=BiblioBazaar|year=2009|isbn=1110753438|page=68}}</ref>
 
 
Fragments of text during this period indicate that Arabs adopted the [[Trigonometric function|sine function]] (inherited from [[Indian mathematics|Indian trigonometry]]) instead of the [[chord (geometry)|chord]]s of [[Arc (geometry)|arc]] used in Hellenistic mathematics.<ref name=Dallal162/> Another Indian influence was an approximate formula used for [[time]]keeping by Muslim astronomers.<ref>{{Harv|King|2002|p=240}}</ref>
 
 
[[Image:Almagest.jpg|thumb|A page from Ptolemy's ''Almagest''.]]
 
Islamic interest in [[astronomy]] ran parallel to the interest in mathematics. Especially noteworthy in this regard was the ''[[Almagest]]'' (c. 150) of the astronomer [[Ptolemy]] (c. 100-178). The ''Almagest'' was a landmark work in its field, assembling, as [[Euclid]]'s ''[[Euclid's Elements|Elements]]'' had previously done with geometrical works, all extant knowledge in the field of astronomy that was known to the author. This work was originally known as ''The Mathematical Composition'', but after it had come to be used as a text in astronomy, it was called ''The Great Astronomer''. The Islamic world called it ''The Greatest'' prefixing the Greek work ''megiste'' (greatest) with the article ''al-'' and it has since been known to the world as ''Al-megiste'' or, after popular use in [[Western world|Western]] translation, ''Almagest''.<ref>{{cite web|title=Greek Astronomy|url=http://www.ibiblio.org/expo/vatican.exhibit/exhibit/d-mathematics/Greek_astro.html |accessdate=2008-01-15}}</ref> though much of the ''Almagest'' was incorrect, even in premise, it remained a standard astronomical text in both the Islamic world and [[Europe]] until the [[#Maragha Revolution|Maragha Revolution]] and [[Copernican Revolution]].<ref>{{cite web|url=http://www.daviddarling.info/encyclopedia/A/Almagest.html|title=Almagest|publisher=The Internet Encyclopedia of Science|accessdate=2008-01-15}}</ref> Ptolemy also produced other works, such as ''Optics'', ''[[Harmonica]]'', and some suggest he also wrote ''Tetrabiblon''.
 
 
The ''Almagest'' was a particularly unifying work for its exhaustive lists of astronomical phenomena. He drew up a list of chronological tables of [[Assyria]]n, [[Persian Empire|Persian]], [[Ancient Greece|Greek]], and [[Roman Empire|Roman]] kings for use in reckoning the lapse of time between known astronomical events and fixed dates. In addition to its relevance to calculating accurate calendars, it linked far and foreign cultures together by a common interest in the stars and astrology. The work of Ptolemy was replicated and refined over the years under [[Arab]], [[Persian people|Persian]] and other [[Muslim]] astronomers and astrologers.
 
 
===825-1025===
 
The period throughout the ninth, tenth and early eleventh centuries was one of vigorous investigation, in which the superiority of the [[Ptolemaic system]] of astronomy was accepted and significant contributions made to it. Astronomical research was greatly supported by the [[Abbasid]] [[caliph]] [[al-Mamun]]. [[Baghdad]] and [[Damascus]] became the centers of such activity. The caliphs not only supported this work [[financial]]ly, but endowed the work with formal prestige.<ref>{{MacTutor|id=Sinan|title=Abu Said Sinan ibn Thabit ibn Qurra|date=November 1999|accessdate=2008-01-15}}</ref>
 
 
====Early observational astronomy====
 
[[Image:Abu Abdullah Muhammad bin Musa al-Khwarizmi.jpg|thumb|[[Muhammad ibn Mūsā al-Khwārizmī|Al-Khwarizmi]], the father of [[algebra]] and [[algorithm]]s and a Persian Astronomer, wrote the ''Zij al-Sindh'', the first original [[Zij]] in Islamic astronomy.]]
 
 
In [[observational astronomy]], the first major original Muslim work of astronomy was ''Zij al-Sindh'' by [[Muhammad ibn Mūsā al-Khwārizmī|Al-Khwarizimi]] in 830. The work contains tables for the movements of the sun, the moon and the five planets known at the time. The work is significant as it introduced Indian and Ptolemaic concepts into Islamic sciences. This work also marked the turning point in Islamic astronomy. Hitherto, Muslim astronomers had adopted a primarily research approach to the field, translating works of others and learning already discovered knowledge. Al-Khwarizmi's work marked the beginning of non-traditional methods of study and calculations.<ref>{{Harv|Dallal|1999|p=163}}</ref>
 
 
Between 825 to 835, [[Habash al-Hasib al-Marwazi]] conducted various observations at the Al-Shammisiyyah [[observatory]] in Baghdad, where he estimated a number of geographic and astronomical values.<ref name=Langermann>{{citation|title=The Book of Bodies and Distances of Habash al-Hasib|last=Langermann|first=Y. Tzvi|journal=[[Centaurus (journal)|Centaurus]]|year=1985|volume=28|pages=108–128 [112]}}</ref> He compiled his results in ''The Book of Bodies and Distances'', in which many of his estimates come closer to modern values than any of his predecessors. For example, he estimated the Moon's diameter as 3,037&nbsp;km (equivalent to 1,519&nbsp;km radius) and its distance from the Earth as 215,209 miles, which come close to the currently accepted values of 1,735&nbsp;km radius and 238,857 miles distance, respectively.<ref>{{citation|title=The Book of Bodies and Distances of Habash al-Hasib|last=Langermann|first=Y. Tzvi|journal=[[Centaurus (journal)|Centaurus]]|year=1985|volume=28|pages=108–128 [111]}}</ref>
 
 
In 850, [[Alfraganus|Al-Farghani]] wrote ''Kitab fi Jawani'' ("''A compendium of the science of stars''"). The book primarily gave a summary of Ptolemic cosmography. However, it also corrected Ptolemy's ''Almagest'' based on findings of earlier Iranian astronomers. Al-Farghani gave revised values for the [[Axial tilt|obliquity]] of the [[ecliptic]], the [[precession]]al movement of the [[apogee]]s of the sun and the moon, and the circumference of the earth. The books were widely circulated through the Muslim world, and even translated into [[Latin]].<ref>{{Harv|Dallal|1999|p=164}}</ref>
 
 
[[Muhammad ibn Jābir al-Harrānī al-Battānī]] (Albatenius) (853-929) produced "improved tables of the orbits of the sun and the moon" that "comprise his discovery that the direction of the sun's [[Orbital eccentricity|eccentric]] as recorded by Ptolemy was changing," which in modern astronomy is equivalent to the Earth moving in an [[elliptical orbit]] around the Sun.<ref>{{Harv|Singer|1959|p=151}} ([[cf.]] {{Harv|Zaimeche|2002}})</ref> His times for the [[new moon]], lengths for the [[solar year]] and [[sidereal year]], prediction of [[eclipse]]s, and work on the phenomenon of [[parallax]], carried astronomers "to the verge of [[Special relativity|relativity]] and the [[space age]]."<ref>{{Harv|Wickens|1976|}} ([[cf.]] {{Harv|Zaimeche|2002}})</ref> Around the same time, Yahya Ibn Abi Mansour carried out extensive observations and tests, and wrote the ''Al-[[Zij]] al-Mumtahan'', in which he completely revised the ''Almagest'' values.<ref>{{citation|title=23rd Annual Conference on the History of Arabic Science|date=October 2001|publisher=[[Aleppo]], [[Syria]]}} ([[cf.]] {{Harv|Zaimeche|2002}})</ref>
 
 
[[Image:Book Al Sufi.jpg|thumb|left|[[Azophi]]'s ''[[Book of Fixed Stars]]'', which described more than a thousand stars in detail and gave the first descriptions on the [[Andromeda Galaxy]] and [[Large Magellanic Cloud]]. The constellation pictured here is [[Sagittarius (constellation)|Sagittarius]].]]
 
 
In the 10th century, [[Abd al-Rahman al-Sufi]] (Azophi) carried out observations on the [[star]]s and described their positions, [[apparent magnitude|magnitudes]], brightness, and [[colour]] and drawings for each constellation in his ''[[Book of Fixed Stars]]'' (964). He also gave the first descriptions and pictures of "A Little Cloud" now known as the [[Andromeda Galaxy]]. He mentions it as lying before the mouth of a Big Fish, an Arabic [[constellation]]. This "cloud" was apparently commonly known to the [[Isfahan (city)|Isfahan]] astronomers, very probably before 905 AD.<ref name="NSOG">{{cite book
 
|last= Kepple
 
|first= George Robert
 
|coauthors= Glen W. Sanner
 
|title= The Night Sky Observer's Guide, Volume 1
 
|publisher= Willmann-Bell, Inc.
 
|year= 1998
 
|isbn= 0-943396-58-1
 
|page=18
 
}}</ref> The first recorded mention of the [[Large Magellanic Cloud]] was also given by Abd Al-Rahman al-Sufi.<ref name="obspm">{{cite web
 
| title=Observatoire de Paris (Abd-al-Rahman Al Sufi)
 
| url=http://messier.obspm.fr/xtra/Bios/alsufi.html
 
| accessdate=2007-04-19 }}</ref><ref name="obspm2">{{cite web
 
| title=Observatoire de Paris (LMC)
 
| url=http://messier.obspm.fr/xtra/ngc/lmc.html
 
| accessdate=2007-04-19 }}</ref>
 
 
[[Ibn Yunus]] observed more than 10,000 entries for the sun's position for many years using a large [[astrolabe]] with a diameter of nearly 1.4 meters. His observations on [[eclipse]]s were still used centuries later in [[Simon Newcomb]]'s investigations on the motion of the moon, while his other observations inspired [[Laplace]]'s ''Obliquity of the Ecliptic'' and ''Inequalities of Jupiter and Saturn''.<ref name=Zaimeche>{{Harv|Zaimeche|2002}}</ref> [[Abu-Mahmud al-Khujandi]] relatively accurately computed the [[axial tilt]] to be 23°32'19" (23.53°).<ref>{{Citation|first=Richard P.|last=Aulie|date=March 1994|title=Al-Ghazali Contra Aristotle: An Unforeseen Overture to Science In Eleventh-Century Baghdad|journal=Perspectives on Science and Christian Faith|volume=45|pages=26–46}} ([[cf.]] {{cite web|url=http://www.1001inventions.com/index.cfm?fuseaction=main.viewSection&intSectionID=441|title=References
 
|publisher=1001 Inventions|accessdate=2008-01-22}})</ref>
 
 
In 1006, the [[Egypt]]ian astronomer [[Ali ibn Ridwan]] observed [[SN 1006]], the brightest [[supernova]] in recorded history, and left a detailed description of the temporary star. He says that the object was two to three times as large as the disc of [[Venus]] and about one-quarter the brightness of the [[Moon]], and that the star was low on the southern horizon. Monks at the [[Benedictine]] abbey at [[Abbey of St. Gall|St. Gall]] later corroborated bin Ridwan's observations as to magnitude and location in the sky.
 
 
====Early heliocentric models====
 
{{see also|Islamic cosmology}}
 
 
The [[Babylonian astronomy|Babylonian astronomer]], [[wikipedia:Seleucus of Seleucia|Seleucus of Seleucia]] developed a [[Heliocentrism|heliocentric]] model in the 2nd century BC, wrote a work that was later translated into Arabic. A fragment of his work has survived only in Arabic translation, which was later referred to by the [[Iranian philosophy|Persian philosopher]] [[Muhammad ibn Zakariya al-Razi]] (865-925).<ref>{{citation|title=Studies in Arabic versions of Greek texts and in mediaeval science|volume=2|author=[[Shlomo Pines]]|publisher=[[Brill Publishers]]|year=1986|isbn=9652236268|pages=viii & 201–17}}</ref>
 
 
[[Jafar al Sadiq]] (702-765) proposed a heliocentric theory. He refuted the [[geocentric model]] of the [[universe]] common at the time, in which the [[Earth]] is not moving and the [[Sun]], [[Moon]] and the [[planet]]s are orbiting around it. He was the first to refute [[Ptolemy]]'s theory of the Sun having two movements, one going round the Earth in one year and the other going round the Earth in 24 hours causing [[day]] and [[night]]. Al-Sadiq argued that if the Sun is moving round the Earth in one year, it cannot suddenly change its course and go round the Earth in one day. He suggested that this could be explained with a [[heliocentrism|heliocentric theory]] in which the [[Earth's rotation|Earth rotates]] about its own axis and around the Sun.<ref name=Strasburg>Reseach Committee of [[University of Strasbourg|Strasburg University]], ''Imam Jafar Ibn Muhammad As-Sadiq A.S. The Great Muslim Scientist and Philosopher'', translated by Kaukab Ali Mirza, 2000. Willowdale Ont. ISBN 0969949014.</ref>
 
 
In the late ninth century, [[Ja'far ibn Muhammad Abu Ma'shar al-Balkhi]] (Albumasar) developed a planetary model which some have interpreted as a heliocentric model. This is due to his [[orbit]]al revolutions of the planets being given as heliocentric revolutions rather than [[Geocentric model|geocentric]] revolutions, and the only known planetary theory in which this occurs is in the heliocentric theory. His work on planetary theory has not survived, but his astronomical data was later recorded by al-Hashimi, [[Abū Rayhān al-Bīrūnī]] and [[al-Sijzi]].<ref>[[Bartel Leendert van der Waerden]] (1987). "The Heliocentric System in Greek, Persian and Hindu Astronomy", ''Annals of the New York Academy of Sciences'' '''500''' (1), 525–545 [534-537].</ref> In the tenth century, the [[Brethren of Purity]] wrote the ''[[Encyclopedia of the Brethren of Purity]]'', in which some verses have been interpreted as implying a heliocentric model, particularly a verse in the ''Rasa'il'' (II, 30) which states:<ref>{{citation|title=Pages of Medieval Mideastern History|author=Eloise Hart|journal=[[Sunrise (magazine)|Sunrise]]|volume=22|date=April-May 1973|url=http://www.theosociety.org/pasadena/sunrise/22-72-3/rel-elo2.htm|accessdate=2010-03-26}}</ref>
 
 
{{quote|"...in so far as the sun is to the heavens what the king is to his kingdom and the planets are to it what soldiers, auxiliaries, and subjects generally are to the king, and the spheres are like regions and the constellations like countries and the degrees and minutes like towns, it was enjoined by divine wisdom that it should be located at the center of the universe."}}
 
 
In the tenth century, the [[Brethren of Purity]] published the ''[[Encyclopedia of the Brethren of Purity]]'', in which a heliocentric view of the universe is expressed in a section on [[cosmology]]:<ref>{{Harv|Nasr|1993|p=77}}</ref>
 
 
{{quote|"God has placed the Sun at the center of the Universe just as the capital of a country is placed in its middle and the ruler's palace at the center of the city."}}
 
 
In the early eleventh century, [[al-Biruni]] had met several Indian scholars who believed in a heliocentric system. In his ''Indica'', he discusses the theories on the [[Earth's rotation]] supported by [[Brahmagupta]] and other [[Indian astronomy|Indian astronomers]], while in his ''Canon Masudicus'', al-Biruni writes that [[Aryabhata]]'s followers assigned the first movement from east to west to the Earth and a second movement from west to east to the fixed stars. Al-Biruni also wrote that [[al-Sijzi]] also believed the Earth was moving and invented an [[astrolabe]] called the "Zuraqi" based on this idea:<ref name=Nasr>{{Harv|Nasr|1993|pp=135-136}}</ref>
 
 
{{quote|"I have seen the astrolabe called Zuraqi invented by Abu Sa'id Sijzi. I liked it very much and praised him a great deal, as it is based on the idea entertained by some to the effect that the motion we see is due to the Earth's movement and not to that of the sky. By my life, it is a problem difficult of solution and refutation. [...] For it is the same whether you take it that the Earth is in motion or the sky. For, in both cases, it does not affect the Astronomical Science. It is just for the physicist to see if it is possible to refute it."}}
 
 
In his ''Indica'', al-Biruni briefly refers to his work on the refutation of [[heliocentrism]], the ''Key of Astronomy'', which is now lost:<ref name=Nasr/>
 
 
{{quote|"The most prominent of both modern and ancient astronomers have deeply studied the question of the moving earth, and tried to refute it. We, too, have composed a book on the subject called ''Miftah 'ilm al-hai'ah'' (''Key of Astronomy''), in which we think we have surpassed our predecessors, if not in the words, at all events in the matter."}}
 
 
====Temporal finitism====
 
{{Main|Temporal finitism}}
 
{{See also|Islamic cosmology|Early Islamic philosophy}}
 
 
In contrast to ancient [[Greek philosophy|Greek philosophers]] who believed that the [[universe]] had an infinite past with no beginning, [[Medieval philosophy|medieval philosophers]] and [[Theology|theologians]] developed the concept of the universe having a finite past with a beginning (see [[Temporal finitism]]). This view was inspired by the [[creation myth]] shared by the three [[Abrahamic religions]]: [[Judaism]], [[Christianity]] and [[Islam]]. The [[Christian philosophy|Christian philosopher]], [[John Philoponus]], presented the first such argument against the ancient Greek notion of an infinite past. His arguments were adopted by many most notably; [[Early Islamic philosophy|early Muslim philosopher]], [[Al-Kindi]] (Alkindus); the [[Jewish philosophy|Jewish philosopher]], [[Saadia Gaon]] (Saadia ben Joseph); and the [[Islamic theology|Muslim theologian]], [[Al-Ghazali]] (Algazel). They used two logical arguments against an infinite past, the first being the "argument from the impossibility of the existence of an actual infinite", which states:<ref name=Craig>{{citation|title=Whitrow and Popper on the Impossibility of an Infinite Past|first=William Lane|last=Craig|journal=The British Journal for the Philosophy of Science|volume=30|issue=2|date=June 1979|pages=165–170 [165–6]|doi=10.1093/bjps/30.2.165}}</ref>
 
 
:"An actual infinite cannot exist."
 
:"An infinite temporal regress of events is an actual infinite."
 
:".•. An infinite temporal regress of events cannot exist."
 
 
The second argument, the "argument from the impossibility of completing an actual infinite by successive addition", states:<ref name=Craig/>
 
 
:"An actual infinite cannot be completed by successive addition."
 
:"The temporal series of past events has been completed by successive addition."
 
:".•. The temporal series of past events cannot be an actual infinite."
 
 
Both arguments were adopted by later Christian philosophers and theologians, and the second argument in particular became more famous after it was adopted by [[Immanuel Kant]] in his thesis of the first antimony concerning [[time]].<ref name=Craig/>
 
 
In the 12th century, [[Fakhr al-Din al-Razi]] presents an argument for [[Islamic creationism|the creation]] of a [[Temporal finitism|temporally finite]] universe, based upon the ideas of [[Motion (physics)|motion]] and [[Rest (physics)|rest]]. He describes the opposing arguments for an eternal universe with eternal bodies, and then argues that had a body (''jism'') "been eternal, in eternity it would have been either in motion or at rest." According to al-Razi, "both alternatives are absurd," therefore, a "body cannot be eternal."<ref>{{citation|title=Fakhr al-Dīn al-Rāzī and Thomas Aquinas on the question of the eternity of the world|author=Muammer İskenderoğlu|publisher=[[Brill Publishers]]|year=2002|isbn=9004124802|page=110}}</ref>
 
 
====Experimental astronomy, astrophysics, celestial mechanics====
 
In the 9th century, the eldest [[Banū Mūsā]] brother, [[Ja'far Muhammad ibn Mūsā ibn Shākir]], made significant contributions to [[Islamic physics|astrophysics]] and [[celestial mechanics]]. He was the first to hypothesize that the heavenly bodies and [[celestial spheres]] are subject to the same [[Physical law|laws of physics]] as [[Earth]], unlike the ancients who believed that the celestial spheres followed their own set of physical laws different from that of Earth.<ref>{{Harv|Saliba|1994a|p=116}}</ref> In his ''Astral Motion'' and ''The Force of Attraction'', Muhammad ibn Musa also proposed that there is a [[force]] of [[Gravitation|attraction]] between [[Astronomical object|heavenly bodies]],<ref>{{citation|first=K. A.|last=Waheed|year=1978|title=Islam and The Origins of Modern Science|page=27|publisher=Islamic Publication Ltd., [[Lahore]]}}</ref> foreshadowing [[Newton's law of universal gravitation]].<ref>{{Harv|Briffault|1938|p=191}}</ref>
 
 
In the 10th century, [[Muhammad ibn Jābir al-Harrānī al-Battānī]] (Albatenius) (853-929) introduced the idea of [[Experiment|testing]] "past observations by means of new ones".<ref>{{Harv|Huff|2003|p=57}}</ref> This led to the use of exacting [[empirical]] observations and experimental techniques by Muslim astronomers from the eleventh century onwards.<ref>{{Harv|Huff|2003|p=326}}</ref>
 
 
In the early 11th century, [[Ibn al-Haytham]] (Alhazen) wrote the ''Maqala fi daw al-qamar'' (''On the Light of the Moon'') some time before 1021. This was the first attempt successful at combining mathematical astronomy with [[physics]] and the earliest attempt at applying the [[Scientific method|experimental method]] to astronomy and [[astrophysics]]. He disproved the universally held opinion that the [[moon]] reflects [[sunlight]] like a [[mirror]] and correctly concluded that it "emits light from those portions of its surface which the [[sun]]'s light strikes." In order to prove that "light is emitted from every point of the moon's illuminated surface," he built an "ingenious [[experiment]]al device." Ibn al-Haytham had "formulated a clear conception of the relationship between an ideal mathematical model and the complex of observable phenomena; in particular, he was the first to make a systematic use of the method of varying the experimental conditions in a constant and uniform manner, in an experiment showing that the [[radiance|intensity]] of the light-spot formed by the projection of the [[moonlight]] through two small [[aperture]]s onto a screen diminishes constantly as one of the apertures is gradually blocked up."<ref name=Toomer>{{citation|first=G. J.|last=Toomer|title=Review: ''Ibn al-Haythams Weg zur Physik'' by Matthias Schramm|journal=[[Isis (journal)|Isis]]|volume=55|issue=4|date=December 1964|pages=463–465 [463–4]|doi=10.1086/349914}}</ref>
 
 
Ibn al-Haytham, in his ''[[Book of Optics]]'' (1021), was also the first to discover that the [[celestial spheres]] do not consist of [[solid]] matter, and he also discovered that the heavens are less dense than the air. These views were later repeated by [[Witelo]] and had a significant influence on the [[Copernican heliocentrism|Copernican]] and [[Tychonic system]]s of astronomy.<ref>{{Harv|Rosen|1985|pp=19-20 & 21}}</ref>
 
 
Ibn al-Haytham also refuted [[Aristotle]]'s view on the Milky Way galaxy. Aristotle believed the Milky Way to be caused by "the ignition of the fiery exhalation of some stars which were large, numerous and close together" and that the "ignition takes place in the upper part of the [[atmosphere]], in the [[Sublunary sphere|region of the world which is continuous with the heavenly motions]]."<ref name=Montada>{{cite web|author=Josep Puig Montada|title=Ibn Bajja|publisher=[[Stanford Encyclopedia of Philosophy]]|url=http://plato.stanford.edu/entries/ibn-bajja|date=September 28, 2007|accessdate=2008-07-11}}</ref> Ibn al-Haytham refuted this by making the first attempt at observing and measuring the Milky Way's [[parallax]],<ref>{{citation|title=Great Muslim Mathematicians|first=Mohaini|last=Mohamed|year=2000|publisher=Penerbit UTM|isbn=9835201579|pages=49–50}}</ref> and he thus "determined that because the Milky Way had no parallax, it was very remote from the [[earth]] and did not belong to the atmosphere."<ref>{{cite web|title=Popularisation of Optical Phenomena: Establishing the First Ibn Al-Haytham Workshop on Photography|author=Hamid-Eddine Bouali, Mourad Zghal, Zohra Ben Lakhdar|publisher=The Education and Training in Optics and Photonics Conference|year=2005|url=http://spie.org/etop/ETOP2005_080.pdf|accessdate=2008-07-08|format=PDF}}</ref>
 
 
Also in the early 11th century, [[Abū Rayhān al-Bīrūnī]] introduced the [[Scientific method|experimental method]] into astronomy and was the first to conduct elaborate [[experiment]]s related to astronomical phenomena.<ref name=Zahoor/> He discovered the [[Milky Way]] [[galaxy]] to be a collection of numerous [[Nebula|nebulous]] [[star]]s.<ref>{{MacTutor Biography|id=Al-Biruni|title=Abu Rayhan Muhammad ibn Ahmad al-Biruni}}</ref> In [[Afghanistan]], he observed and described the [[solar eclipse]] on April 8, 1019, and the [[lunar eclipse]] on September 17, 1019, in detail, and gave the exact [[latitude]]s of the stars during the lunar eclipse.<ref name=Zahoor>{{cite web|author=Dr. A. Zahoor|year=1997|url=http://www.unhas.ac.id/~rhiza/saintis/biruni.html|title=Abu Raihan Muhammad al-Biruni|publisher=[[Hasanuddin University]]|archiveurl=
 
http://209.85.135.104/search?sourceid=navclient-ff&ie=UTF-8&q=cache%3Ahttp%3A%2F%2Fwww.unhas.ac.id%2F~rhiza%2Fsaintis%2Fbiruni.html
 
|archivedate=2008-01-18}}</ref>
 
 
===1025-1450===
 
During this period, a distinctive Islamic system of astronomy flourished. It was Greek tradition to separate mathematical astronomy (as typified by [[Ptolemy]]) from philosophical cosmology (as typified by [[Aristotle]]). Muslim scholars developed a program of seeking a physically real configuration (''hay'a'') of the universe, that would be consistent with both [[mathematics|mathematical]] and [[physics|physical]] principles. Within the context of this ''hay'a'' tradition, Muslim astronomers began questioning technical details of the [[Ptolemaic system]] of astronomy.<ref>{{Harv|Sabra|1998|pp=293-8}}</ref> Most of these criticisms, however, continued to follow the Ptolemaic astronomical [[paradigm]], remaining within the [[geocentrism|geocentric]] framework.<ref>{{cite web|author=Dennis Duke|url=http://people.scs.fsu.edu/~dduke/arabmars.html|title=Arabic Models for outer Planets and Venus|accessdate=2008-01-22}}</ref> As the historian of astronomy, [[A. I. Sabra]], noted:
 
 
{{quote|"All Islamic astronomers from [[Thabit ibn Qurra]] in the ninth century to [[Ibn al-Shatir]] in the fourteenth, and all natural philosophers from [[al-Kindi]] to [[Averroes]] and later, are known to have accepted what Kuhn has called the "two-sphere universe" ...&mdash;the Greek picture of the world as consisting of two spheres of which one, the [[celestial spheres|celestial sphere]] made up of a special element called [[Aether (classical element)|aether]], concentrically envelops the other, where the [[classical elements|four elements]] of earth, water, air, and fire reside."<ref>{{Harv|Sabra|1998|pp=317-18}}</ref>}}
 
 
Some Muslim astronomers, however, most notably [[Abū Rayhān al-Bīrūnī]] and [[Nasīr al-Dīn al-Tūsī]], discussed whether the Earth moved and considered how this might be consistent with astronomical computations and physical systems.<ref>{{Harv|Ragep|Teresi|Hart|2002}}</ref> Several other Muslim astronomers, most notably those following the [[Maragheh observatory|Maragha school]] of astronomy, developed non-Ptolemaic planetary models within a geocentric context that were later adapted by the [[Copernican heliocentrism|Copernican model]] in a [[heliocentrism|heliocentric]] context.
 
 
====Refutations of astrology====
 
{{See also|Islamic astrology}}
 
 
The first [[Semantics|semantic]] distinction between astronomy and [[astrology]] was given by the [[Persian people|Persian]] astronomer [[Abū Rayhān al-Bīrūnī|Abu Rayhan al-Biruni]] in the 11th century,<ref>S. Pines (September 1964). "The Semantic Distinction between the Terms Astronomy and Astrology according to al-Biruni", ''Isis'' '''55''' (3): 343-349.</ref> though he himself refuted astrology in another work. The study of astrology was also refuted by other Muslim astronomers at the time, including [[al-Farabi]], [[Ibn al-Haytham]], [[Avicenna]] and [[Averroes]]. Their reasons for refuting astrology were often due to both scientific (the methods used by astrologers being [[conjectural]] rather than [[empirical]]) and religious (conflicts with orthodox [[Ulema|Islamic scholars]]) reasons.<ref>{{Harv|Saliba|1994b|pp=60 & 67-69}}</ref>
 
 
[[Ibn Qayyim Al-Jawziyya]] (1292–1350), in his ''Miftah Dar al-SaCadah'', used [[empirical]] arguments in astronomy in order to refute the practice of astrology and [[divination]].<ref>{{citation|title=Ibn Qayyim al-Jawziyyah: A Fourteenth Century Defense against Astrological Divination and Alchemical Transmutation|first=John W.|last=Livingston|journal=Journal of the American Oriental Society|volume=91|issue=1|year=1971|pages=96–103|doi=10.2307/600445}}</ref> He recognized that the [[star]]s are much larger than the [[planet]]s, and that [[Mercury (planet)|Mercury]] is the smallest planet known to them, and thus argued:<ref name=Livingston>{{citation|title=Ibn Qayyim al-Jawziyyah: A Fourteenth Century Defense against Astrological Divination and Alchemical Transmutation|first=John W.|last=Livingston|journal=Journal of the American Oriental Society|volume=91|issue=1|year=1971|pages=96–103 [99]|doi=10.2307/600445}}</ref>
 
 
{{quote|"And if you astrologers answer that it is precisely because of this distance and smallness that their influences are negligible, then why is it that you claim a great influence for the smallest heavenly body, Mercury? Why is it that you have given an influence to al-Ra's and al-Dhanab, which are two imaginary points [ascending and descending nodes]?"}}
 
 
Al-Jawziyya also recognized the [[Milky Way]] [[galaxy]] as "a myriad of tiny stars packed together in the sphere of the fixed stars" and thus argued that "it is certainly impossible to have knowledge of their influences."<ref name=Livingston/>
 
 
====Astrophysics and celestial mechanics====
 
In [[astrophysics]] and [[celestial mechanics]], [[Abū Rayhān al-Bīrūnī]] described the Earth's [[gravitation]] as:<ref name=Khwarizm/>
 
{{quote|"The attraction of all things towards the centre of the earth."}}
 
 
Al-Biruni also discovered that gravity exists within the [[Astronomical object|heavenly bodies]] and [[celestial spheres]], and he criticized the [[Aristotelian theory of gravity|Aristotelian]] views of them not having any [[Aristotelian_theory_of_gravity#Gravity|levity or gravity]] and of [[circular motion]] being an [[Intrinsic and extrinsic properties|innate property]] of the heavenly bodies.<ref>{{Harv|Iqbal|Berjak|2003}}</ref>
 
 
In 1121, [[al-Khazini]], in his treatise ''The Book of the Balance of Wisdom'', states:<ref name=Zaimeche7>{{Harv|Zaimeche|2002|p=7}}</ref>
 
{{quote|"For each heavy body of a known weight positioned at a certain distance from the centre of the universe, its gravity depends on the remoteness from the centre of the universe. For that reason, the gravities of bodies relate as their distances from the centre of the universe."}}
 
 
Al-Khazini was thus the first to propose the theory that the [[Gravitation|gravity]] or [[gravitational potential energy]] of a body varies depending on its distances from the centre of the Earth. This phenomenon was not proven until the 18th century, following [[Newton's law of universal gravitation]].<ref name=Zaimeche7/>
 
 
Also in the 12th century, [[Fakhr al-Din al-Razi]] participated in the debate among Islamic scholars over whether the [[celestial spheres]] or orbits (''falak'') are "to be considered as real, concrete physical bodies" or "merely the abstract circles in the heavens traced out year in and year out by the various stars and planets." He points out that many astronomers prefer to see them as solid spheres "on which the stars turn," while others, such as the Islamic scholar Dahhak, view the celestial sphere as "not a body but merely the abstract orbit traced by the stars." Al-Razi himself remains "undecided as to which [[Celestial mechanics|celestial models]], concrete or abstract, most conform with external reality," and notes that "there is no way to ascertain the characteristics of the heavens," whether by "observable" evidence or by authority (''al-khabar'') of "[[Qur'an|divine revelation]] or [[Sunnah|prophetic traditions]]." He concludes that "astronomical models, whatever their utility or lack thereof for ordering the heavens, are not founded on sound rational proofs, and so no intellectual commitment can be made to them insofar as description and explanation of celestial realities are concerned."<ref name=Setia/>
 
 
The theologian Adud al-Din al-Iji (1281–1355), under the influence of the [[Ash'ari]] doctrine of [[occasionalism]], rejected many [[On the Heavens|Aristotelian cosmological]] theories that he insisted were purely conjectural and hypothetical, including the Aristotelian and [[Geocentric model#Ptolemaic system|Ptolemaic]] principle of [[uniform circular motion]] in the heavenly bodies,<ref name=Huff-175>{{Harv|Huff|2003|p=175}}</ref> and maintained that the celestial spheres were "imaginary things" that did not physically exist.<ref name=Ragep2/>
 
 
====Beginning of hay'a program====
 
[[File:Ibn al-Haytham.png|thumb|[[Ibn al-Haytham]] (Alhacen) was a pioneer of the Muslim ''haya'' tradition of astronomy, presented the first critique and reform of [[Ptolemy]]'s model, and introduced [[experiment]]ation to [[astrophysics]].]]
 
 
Between 1025 and 1028, [[Ibn al-Haytham]] ([[Latin]]ized as Alhazen), began the ''hay'a'' tradition of Islamic astronomy with his ''Al-Shuku ala Batlamyus'' (''Doubts on Ptolemy''). While maintaining the physical reality of the [[geocentric model]], he was the first to criticize [[Ptolemy]]'s astronomical system, which he criticized on [[empirical]], [[observation]]al and [[experiment]]al grounds,<ref>{{Harv|Sabra|1998|p=300}}</ref> and for relating actual physical motions to imaginary mathematical points, lines and circles:
 
{{quote|"Ptolemy assumed an arrangement that cannot exist, and the fact that this arrangement produces in his imagination the motions that belong to the planets does not free him from the error he committed in his assumed arrangement, for the existing motions of the planets cannot be the result of an arrangement that is impossible to exist."<ref>{{citation|url=http://setis.library.usyd.edu.au/stanford/entries/copernicus/index.html
 
|contribution=Nicolaus Copernicus|title=[[Stanford Encyclopedia of Philosophy]]|year=2004|accessdate=2008-01-22}}</ref>}}
 
 
Ibn al-Haytham developed a physical structure of the Ptolemaic system in his ''Treatise on the configuration of the World'', or ''Maqâlah fî ''hay'at'' al-‛âlam'', which became an influential work in the ''hay'a'' tradition.<ref>{{Harv|Langermann|1990|pp=25-34}}</ref> In his ''Epitome of Astronomy'', he insisted that the heavenly bodies "were accountable to the [[Physical law|laws of physics]]."<ref>{{Harv|Duhem|1969|p=28}}</ref>
 
 
In 1038, Ibn al-Haytham described the first non-Ptolemaic configuration in ''The Model of the Motions''. His reform was not concerned with [[cosmology]], as he developed a systematic study of celestial [[kinematics]] that was completely [[geometry|geometric]]. This in turn led to innovative developments in [[infinitesimal]] [[geometry]].<ref>{{Harv|Rashed|2007}}</ref> His reformed model was the first to reject the [[equant]]<ref>{{Harv|Rashed|2007|pp=20 & 53}}</ref> and [[Deferent|eccentrics]],<ref>{{Harv|Rashed|2007|pp=33-4}}</ref> separate [[natural philosophy]] from astronomy, free celestial kinematics from cosmology, and reduce physical entities to geometrical entities. The model also propounded the [[Earth's rotation]] about its axis,<ref>{{Harv|Rashed|2007|pp=20 & 32-33}}</ref> and the centres of motion were geometrical points without any physical significance, like [[Johannes Kepler]]'s model centuries later.<ref>{{Harv|Rashed|2007|pp=51-2}}</ref> Ibn al-Haytham also describes an early version of [[Occam's razor]], where he employs only minimal hypotheses regarding the properties that characterize astronomical motions, as he attempts to eliminate from his planetary model the [[cosmology|cosmological]] hypotheses that cannot be observed from [[Earth]].<ref>{{Harv|Rashed|2007|pp=35-6}}</ref>
 
 
[[Image:Al-Biruni Afghan stamp.jpg|thumb|left|[[Abū al-Rayhān al-Bīrūnī|Al-Biruni]] was the first to conduct elaborate [[experiment]]s related to astronomical phenomena, and he introduced the analysis of the [[acceleration]] of planets, discovered that the motions of the [[Apsis|solar apogee]] and [[precession]] are not identical, discussed the possibility of [[heliocentrism]], and suggested that the [[Earth's rotation]] on its axis would be consistent with his astronomical parameters.]]
 
 
====Early alternative models====
 
In 1030, [[Abū al-Rayhān al-Bīrūnī]] discussed the [[Indian astronomy|Indian planetary theories]] of [[Aryabhata]], [[Brahmagupta]] and [[Varahamihira]] in his ''Ta'rikh al-Hind'' (Latinized as ''Indica''). Biruni stated that [[Brahmagupta]] and others consider that the [[Earth's rotation|earth rotates]] on its axis and Biruni noted that this does not create any mathematical problems.<ref>{{Harv|Nasr|1993|p=135, n. 13}}</ref>
 
 
[[Al-Sijzi|Abu Said al-Sijzi]], a contemporary of al-Biruni, suggested the possible heliocentric movement of the Earth around the Sun, which al-Biruni did not reject.<ref name=Baker>{{Harv|Baker|Chapter|2002}}</ref> Al-Biruni agreed with the [[Earth's rotation]] about its own axis, and while he was initially neutral regarding the [[heliocentrism|heliocentric]] and [[geocentric model]]s,<ref>{{Harv|Marmura|1965}}</ref> he considered heliocentrism to be a philosophical problem.<ref name=Saliba/> He remarked that if the Earth rotates on its axis and moves around the Sun, it would remain consistent with his astronomical parameters:<ref name=Khwarizm/><ref>G. Wiet, V. Elisseeff, P. Wolff, J. Naudu (1975). ''History of Mankind, Vol 3: The Great medieval Civilisations'', p. 649. George Allen & Unwin Ltd, [[UNESCO]].</ref>
 
{{quote|"Rotation of the earth would in no way invalidate astronomical calculations, for all the astronomical data are as explicable in terms of the one theory as of the other. The problem is thus difficult of solution."}}
 
 
In 1031, [[Al-Biruni]] completed his extensive astronomical encyclopaedia ''Kitab al-Qanun al-Mas'udi'' ([[Latin]]ized as ''Canon Mas’udicus''),<ref name=Covington>{{Harv|Covington|2007}}</ref> in which he recorded his astronomical findings and formulated astronomical tables. In it he presented a geocentric model, tabulating the distance of all the [[celestial spheres]] from the central Earth, computed according to the principles of Ptolemy's ''[[Almagest]]''.<ref>{{Harv|Nasr|1993|p=134}}</ref> The book introduces the mathematical technique of analysing the [[acceleration]] of the planets, and first states that the motions of the [[Apsis|solar apogee]] and the [[precession]] are not identical. Al-Biruni also discovered that the distance between the Earth and the Sun is larger than [[Ptolemy]]'s estimate, on the basis that Ptolemy disregarded annular eclipses.<ref name=Khwarizm>{{cite web|url=http://muslimheritage.com/topics/default.cfm?ArticleID=482|title=Khwarizm|publisher=Foundation for Science Technology and Civilisation|accessdate=2008-01-22}}</ref><ref>{{Harv|Saliba|1980|p=249}}</ref>
 
 
In 1070, [[Juzjani, Abu Ubaid|Abu Ubayd al-Juzjani]], a pupil of [[Avicenna]], proposed a non-Ptolemaic configuration in his ''Tarik al-Aflak''. In his work, he indicated the so-called "[[equant]]" problem of the Ptolemic model, and proposed a solution for the problem. He claimed that his teacher Avicenna had also worked out the equant problem.<ref>{{Harv|Sabra|1998|pp=305-306}}</ref>
 
 
[[Omar Khayyam]] (1048-1131) demonstrated that the earth rotates on its axis<ref>{{cite web|url=http://www.physicsoftheuniverse.com/dates.html#Medieval |title=physicsoftheuniverse.com |publisher=physicsoftheuniverse.com |date= |accessdate=2012-09-08}}</ref> by presenting a model of the stars to his contemporary [[al-Ghazali]] in a planetarium.<ref>{{cite web|url=http://www.khayyam.info/english/default.htm#Heliocentric |title=Theory |publisher=Khayyam.info |date= |accessdate=2012-09-08}}</ref> Khayyam believed in heliocentrism, according to [[Edward FitzGerald (poet)|Edward Fitzgerald]]'s popular renderings<ref>Donald and Marilynn Olson (1988), '[http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1988Obs...108..181O&db_key=AST&page_ind=0&data_type=GIF&type=SCREEN_VIEW&classic=YES Zodiac Light, False Dawn, and Omar Khayyam]', The Observatory, vol. 108, p. 181-182</ref> of Khayyam's poetry, in which the first lines are mistranslated with a heliocentric image of the Sun flinging "the Stone that puts the Stars to Flight".<ref>{{cite web|url=http://www.humanistictexts.org/omar_khayyam.htm#_Toc483885355 |title=Rex Pay, 2000 |publisher=Humanistictexts.org |date= |accessdate=2012-09-08}}</ref>
 
 
Allusions to heliocentrism also can be found in the works of Muslim theologians and philosophers such as [[Fakhr al-Din al-Razi]] (b. 1149), [[Al-Zamakhshari]] (b. 1075), and Ottoman [[Sheikh ul-Islam]] [[Ebussuud Efendi]] (b.1490). In his major work ''[[Tafsir al-Kabir (al-Razi)|Tafsir al-Kabir]]'', [[Fakhr al-Din al-Razi]] defends ideas of heliocentrism, with the only difference that the Sun is not mentioned as a static object or as a centre of the Universe:
 
 
{{quote|
 
Even though the Earth is described as a bed in this verse, in the other verse it is portrayed as a sphere. Spherical earth is revolving around the Sun. If questioned "How people and objects can stand on the Earth if the Earth, as a sphere, revolving around the Sun?", my answer will be that the Earth is such a huge sphere where flat surfaces appear."<ref>[[Fakhr al-Din al-Razi]], [[Tafsir al-Kabir (al-Razi)|Tafsir al-Kabir]] 2/95</ref>
 
}}
 
 
[[Al-Zamakhshari]] in his work [[Al-Kashshaaf]]<ref>[[Al-Zamakhshari]], [[Al-Kashshaaf]] 1/125</ref> and [[Ebussuud Efendi]] in [[Irshadu'l-Akli's-Selim]]<ref>[[Ebussuud Efendi]], [[Irshadu'l-Akli's-Selim]] 1/61</ref> provide similar explanations which support heliocentrism.
 
 
====Andalusian Revolt====
 
[[Image:AverroesColor.jpg|thumb|[[Averroes]] rejected the [[Deferent and epicycle|eccentric deferents]] introduced by [[Ptolemy]]. He rejected the [[Ptolemaic model]] and instead argued for a strictly [[concentric]] model of the universe.]]
 
 
In the 11th-12th centuries, astronomers in [[al-Andalus]] took up the challenge earlier posed by Ibn al-Haytham, namely to develop an alternate non-Ptolemaic configuration that evaded the errors found in the [[Geocentric model|Ptolemaic model]].<ref>{{Harv|Saliba|1981|p=219}}</ref> Like Ibn al-Haytham's critique, the anonymous Andalusian work, ''al-Istidrak ala Batlamyus'' (''Recapitulation regarding Ptolemy''), included a list of objections to Ptolemic astronomy. This marked the beginning of the Andalusian school's [[revolt]] against Ptolemaic astronomy, otherwise known as the "Andalusian Revolt".<ref>{{citation|first=A. I.|last=Sabra|author-link=A. I. Sabra|contribution=The Andalusian Revolt Against Ptolemaic Astronomy: Averroes and al-Bitrûjî|pages=233–53|editor-first=Everett|editor-last=Mendelsohn|title=Transformation and Tradition in the Sciences: Essays in honor of I. Bernard Cohen|publisher=[[Cambridge University Press]]}}</ref>
 
 
In the late 11th century, [[Arzachel|al-Zarqali]] (Latinized as Arzachel) discovered that the orbits of the [[planet]]s are [[elliptic orbit]]s and not circular orbits,<ref>[[Robert Briffault]] (1938). ''The Making of Humanity'', p. 190.</ref> though he still followed the Ptolemaic model.
 
 
In the 12th century, [[Averroes]] rejected the [[Deferent and epicycle|eccentric deferents]] introduced by [[Ptolemy]]. He rejected the [[Ptolemaic model]] and instead argued for a strictly [[concentric]] model of the universe. He wrote the following criticism on the Ptolemaic model of planetary motion:<ref name=Gingerich/>
 
 
{{quote|"To assert the existence of an eccentric sphere or an epicyclic sphere is contrary to nature. [...] The astronomy of our time offers no truth, but only agrees with the calculations and not with what exists."}}
 
 
Averroes' contemporary, [[Maimonides]], wrote the following on the planetary model proposed by [[Ibn Bajjah]] (Avempace):
 
 
{{quote|"I have heard that Abu Bakr [Ibn Bajja] discovered a system in which no [[Deferent and epicycle|epicycles]] occur, but [[Eccentricity (mathematics)|eccentric]] spheres are not excluded by him. I have not heard it from his pupils; and even if it be correct that he discovered such a system, he has not gained much by it, for eccentricity is likewise contrary to the principles laid down by Aristotle.... I have explained to you that these difficulties do not concern the astronomer, for he does not profess to tell us the existing properties of the spheres, but to suggest, whether correctly or not, a theory in which the motion of the [[star]]s and planets is uniform and circular, and in agreement with observation."<ref>Bernard R. Goldstein (March 1972). "Theory and Observation in Medieval Astronomy", ''Isis'' '''63''' (1): 39-47 [40-41].</ref>}}
 
 
Ibn Bajjah also proposed the [[Milky Way]] [[galaxy]] to be made up of many stars but that it appears to be a continuous image due to the effect of [[refraction]] in the [[Earth's atmosphere]], citing his observation of the [[Conjunction (astronomy and astrology)|conjunction]] of Jupiter and Mars on 500 [[Islamic calendar|AH]] (1106/1107 AD) as evidence.<ref name=Montada/> Later in the 12th century, his successors [[Ibn Tufail]] and [[Al-Bitruji]] (Alpetragius) were the first to propose planetary models without any [[equant]], [[Deferent and epicycle|epicycles or eccentrics]]. Al-Betrugi was also the first to discover that the planets are [[Luminosity|self-luminous]].<ref>Bernard R. Goldstein (March 1972). "Theory and Observation in Medieval Astronomy", ''Isis'' '''63''' (1): 39-47 [41].</ref> Their configurations, however, were not accepted due to the numerical predictions of the planetary positions in their models being less accurate than that of the Ptolemaic model,<ref name=Gale>{{citation|url=http://www.bookrags.com/research/ptolemaic-astronomy-islamic-planeta-scit-021234
 
|contribution=Ptolemaic Astronomy, Islamic Planetary Theory, and Copernicus's Debt to the Maragha School|title=Science and Its Times|publisher=[[Thomson Gale]]|year=2005-2006|accessdate=2008-01-22}}</ref> mainly because they followed [[Aristotle]]'s notion of perfectly [[uniform circular motion]].
 
 
Al-Bitruji� was later cited by [[Copernicus]] as an influence on his ''De revolutionibus'', "regarding the placement of Venus and Mercury with respect to the sun." [http://www.bowdoin.edu/faculty/r/rgmorris/pdf/scholarly-intermediary-2014.pdf]
 
 
====Maragha Revolution====
 
{{See also|Maragheh observatory|Tusi-couple|Zij-i Ilkhani}}
 
 
The "Maragha Revolution" refers to the [[Maragheh]] school's [[revolution]] against Ptolemaic astronomy. The "Maragha school" was an astronomical tradition beginning in the [[Maragheh observatory]] and continuing with astronomers from the [[Umayyad Mosque|Damascus mosque]] and [[Ulugh Beg Observatory|Samarkand observatory]]. Like their Andalusian predecessors, the Maragha astronomers attempted to solve the [[equant]] problem and produce alternative configurations to the [[Ptolemaic model]]. They were more successful than their Andalusian predecessors in producing non-Ptolemaic configurations which eliminated the equant and eccentrics, were more accurate than the Ptolemaic model in numerically predicting planetary positions, and were in better agreement with [[empirical]] [[observation]]s.<ref name=Saliba-1994>{{Harv|Saliba|1994b|pp=233-234 & 240}}</ref> The most important of the Maragha astronomers included [[Mo'ayyeduddin Urdi]] (d. 1266), [[Nasīr al-Dīn al-Tūsī]] (1201–1274), [[Najm al-Dīn al-Qazwīnī al-Kātibī]] (d. 1277), [[Qotb al-Din Shirazi]] (1236–1311), Sadr al-Sharia al-Bukhari (c. 1347), [[Ibn al-Shatir]] (1304–1375), [[Ali al-Qushji]] (c. 1474), [[al-Birjandi]] (d. 1525) and [[Shams al-Din al-Khafri]] (d. 1550).<ref>{{Harv|Dallal|1999|p=171}}</ref>
 
 
[[Image:Al-Tusi Nasir.jpeg|thumb|left|150px|[[Nasīr al-Dīn al-Tūsī]] resolved significant problems in the [[Geocentric model|Ptolemaic system]] with the [[Tusi-couple]], which later played an important role in the [[Copernican heliocentrism|Copernican model]].]]
 
 
Some have described their achievements in the 13th and 14th centuries as a "Maragha Revolution", "Maragha School Revolution", or "[[Scientific Revolution]] before the [[Renaissance]]". An important aspect of this revolution included the realization that astronomy should aim to describe the behavior of [[Physical body|physical bodies]] in [[Islamic mathematics|mathematical]] language, and should not remain a mathematical [[hypothesis]], which would only save the [[phenomena]]. The Maragha astronomers also realized that the [[On the Heavens|Aristotelian]] view of [[Motion (physics)|motion]] in the universe being only circular or [[linear]] was not true, as the [[Tusi-couple]] showed that linear motion could also be produced by applying [[circular motion]]s only.<ref>{{Harv|Saliba|1994b|pp=245, 250, 256-257}}</ref>
 
 
Unlike the ancient Greek and Hellenistic astronomers who were not concerned with the coherence between the mathematical and physical principles of a planetary theory, Islamic astronomers insisted on the need to match the mathematics with the real world surrounding them,<ref>{{citation|first=George|last=Saliba|author-link=George Saliba|date=Autumn 1999|title=Seeking the Origins of Modern Science?|journal=BRIIFS|volume=1|issue=2|url=http://www.riifs.org/review_articles/review_v1no2_sliba.htm |accessdate=2008-01-25}}</ref> which gradually evolved from a reality based on [[Aristotelian physics]] to one based on an empirical and mathematical [[physics]] after the work of [[Ibn al-Shatir]]. The Maragha Revolution was thus characterized by a shift away from the philosophical foundations of [[On the Heavens|Aristotelian cosmology]] and [[Ptolemaic astronomy]] and towards a greater emphasis on the empirical observation and [[Islamic mathematics|mathematization]] of astronomy and of [[nature]] in general, as exemplified in the works of Ibn al-Shatir, al-Qushji, al-Birjandi and al-Khafri.<ref>{{Harv|Saliba|1994b|pp=42 & 80}}</ref><ref>{{citation|first=Ahmad|last=Dallal|year=2001-2002|title=The Interplay of Science and Theology in the Fourteenth-century Kalam|publisher=From Medieval to Modern in the Islamic World, Sawyer Seminar at the [[University of Chicago]] |url=http://humanities.uchicago.edu/orgs/institute/sawyer/archive/islam/dallal.html |accessdate=2008-02-02}}</ref><ref>{{Harv|Huff|2003|pp=217-8}}</ref>
 
 
[[Image:Shatir500.jpg|thumb|right|[[Ibn al-Shatir]]'s model for the appearances of [[Mercury (planet)|Mercury]], showing the multiplication of [[Deferent and epicycle|epicycle]]s using the [[Tusi-couple]], thus eliminating the Ptolemaic eccentrics and [[equant]].]]
 
 
Other achievements of the Maragha school include the first empirical observational evidence for the [[Earth's rotation]] on its axis by al-Tusi and al-Qushji,<ref name=Ragep/> the separation of [[natural philosophy]] from astronomy by Ibn al-Shatir and al-Qushji,<ref name=Ragep2>{{Harv|Ragep|2001b}}</ref> the rejection of the Ptolemaic model on empirical rather than [[philosophical]] grounds by Ibn al-Shatir,<ref name=Saliba-1994/> and the development of a non-Ptolemaic model by Ibn al-Shatir that was mathematically identical to the [[Copernican heliocentrism|heliocentric Copernical model]].<ref>{{Harv|Saliba|1994b|pp=254 & 256-257}}</ref>
 
 
[[Mo'ayyeduddin Urdi]] (d. 1266) was the first of the Maragheh astronomers to develop a non-Ptolemaic model, and he proposed a new theorem, the "Urdi lemma".<ref>{{Harv|Saliba|1979}}</ref> [[Nasīr al-Dīn al-Tūsī]] (1201–1274) resolved significant problems in the Ptolemaic system by developing the [[Tusi-couple]] as an alternative to the physically problematic [[equant]] introduced by Ptolemy,<ref name=Gill>{{Harv|Gill|2005}}</ref> and conceived a plausible model for [[ellipse|elliptical]] orbits.<ref name=Covington/> Tusi's student [[Qotb al-Din Shirazi]] (1236–1311), in his ''The Limit of Accomplishment concerning Knowledge of the Heavens'', discussed the possibility of [[heliocentrism]]. [[Najm al-Dīn al-Qazwīnī al-Kātibī|Al-Qazwīnī al-Kātibī]] (d. 1277), who also worked at the Maragheh observatory, in his ''Hikmat al-'Ain'', wrote an argument for a heliocentric model, though he later abandoned the idea.<ref name=Baker/>
 
 
[[Image:Ghotb2.jpg|thumb|left|Medieval manuscript by [[Qutb al-Din al-Shirazi]] depicting an epicyclic planetary model.]]
 
 
[[Ibn al-Shatir]] (1304–1375) of [[Damascus]], in ''A Final Inquiry Concerning the Rectification of Planetary Theory'', incorporated the Urdi lemma, and eliminated the need for an equant by introducing an extra epicycle (the Tusi-couple), departing from the Ptolemaic system in a way that was mathematically identical to what [[Nicolaus Copernicus]] did in the 16th century. Unlike previous astronomers before him, Ibn al-Shatir was not concerned with adhering to the theoretical principles of [[natural philosophy]] or Aristotelian [[cosmology]], but rather to produce a model that was more consistent with [[empirical]] observations. For example, it was Ibn al-Shatir's concern for observational accuracy which led him to eliminate the epicycle in the Ptolemaic [[Sun|solar]] model and all the eccentrics, epicycles and equant in the Ptolemaic [[Lunar theory|lunar model]]. His model was thus in better agreement with empirical [[observation]]s than any previous model,<ref name=Saliba-1994/> and was also the first that permitted empirical [[Experiment|testing]].<ref>Y. M. Faruqi (2006). "Contributions of Islamic scholars to the scientific enterprise", ''International Education Journal'' '''7''' (4): 395-396.</ref> His work thus marked a turning point in astronomy, which may be considered a "Scientific Revolution before the Renaissance".<ref name=Saliba-1994/> His rectified model was later adapted into a [[Copernican heliocentrism|heliocentric model]] by Copernicus,<ref name=Gill/> which was mathematically achieved by reversing the direction of the last vector connecting the Earth to the Sun.<ref name=Saliba>{{Harv|Saliba|1999}}</ref> In the published version of his masterwork, ''[[De revolutionibus orbium coelestium]]'', Copernicus also cites the theories of [[al-Battani]], [[Arzachel]] and [[Averroes]] as influences,<ref name=Covington/> while the works of [[Ibn al-Haytham]] and [[al-Biruni]] were also known in Europe at the time. It has also been suggested that the Byzantine Greek scholar [[wikipedia:Gregory Chioniades|Gregory Chioniades]] introduced the Tusi-couple to Europe. [http://www.bowdoin.edu/faculty/r/rgmorris/pdf/scholarly-intermediary-2014.pdf]
 
 
An area of active discussion in the Maragheh school, and later the [[Samarkand]] and [[Istanbul]] observatories, was the possibility of the [[Earth's rotation]]. Supporters of this theory included [[Nasīr al-Dīn al-Tūsī]], Nizam al-Din al-Nisaburi (c. 1311), al-Sayyid al-Sharif al-Jurjani (1339–1413), Ali al-Qushji (d. 1474), and Abd al-Ali [[al-Birjandi]] (d. 1525). Al-Tusi was the first to present empirical observational evidence of the Earth's rotation, using the location of [[comet]]s relevant to the Earth as evidence, which al-Qushji elaborated on with further empirical observations while rejecting Aristotelian [[natural philosophy]] altogether. Both of their arguments were similar to the arguments later used by [[Nicolaus Copernicus]] in 1543 to explain the Earth's rotation (see [[#Astronomical physics and Earth's motion|Astronomical physics and Earth's motion]] section below).<ref name=Ragep>{{Harv|Ragep|2001a}}</ref>
 
 
====Multiverse theory====
 
{{Main|Islamic cosmology}}
 
 
[[Fakhr al-Din al-Razi]] (1149–1209), in dealing with his [[Physics in medieval Islam|conception of physics]] and the physical world in his ''Matalib'', discusses [[Islamic cosmology]] and astronomy. He criticizes the idea of the [[geocentric model|Earth's centrality]] within the universe and "explores the notion of the existence of a [[multiverse]] in the context of his commentary" on the [[Qur'an]]ic verse, "All praise belongs to God, Lord of the Worlds." He raises the question of whether the term "[[world]]s" in this verse refers to "multiple worlds within this single [[universe]] or [[cosmos]], or to many other universes or a multiverse beyond this known universe." In volume 4 of the ''Matalib'', Al-Razi states:<ref name=Setia>{{citation|title=Fakhr Al-Din Al-Razi on Physics and the Nature of the Physical World: A Preliminary Survey|author=Adi Setia|journal=Islam & Science|volume=2|year=2004|url=http://findarticles.com/p/articles/mi_m0QYQ/is_2_2/ai_n9532826/|accessdate=2010-03-02|archiveurl=http://archive.is/AGUX|archivedate=2012-07-10}}</ref>
 
 
{{quote|It is established by evidence that there exists beyond the world a void without a terminal limit (''khala' la nihayata laha''), and it is established as well by evidence that God Most High has power over all contingent beings (''al-mumkinat''). Therefore He the Most High has the power (''qadir'') to create a thousand thousand worlds (''alfa alfi 'awalim'') beyond this world such that each one of those worlds be bigger and more massive than this world as well as having the like of what this world has of the throne (''al-arsh''), the chair (''al-kursiyy''), the heavens (''al-samawat'') and the earth (''al-ard''), and the sun (''al-shams'') and the moon (''al-qamar''). The arguments of the philosophers (''dala'il al-falasifah'') for establishing that the world is one are weak, flimsy arguments founded upon feeble premises.}}
 
 
Al-Razi rejected the [[Aristotelianism|Aristotelian]] and [[Avicennism|Avicennian]] view of the impossibility of multiple worlds or universes. He describes the main Aristotelian arguments against the existence of multiple worlds or universes, pointing out their weaknesses and refuting them. This rejection arose from his affirmation of [[atomism]], as advocated by the [[Ash'ari]] school of [[Islamic theology]], which entails the existence of vacant space in which the atoms move, combine and separate. He discussed more on the issue of the [[Vacuum|void]] in greater detail in volume 5 of the ''Matalib''.<ref name=Setia/> He argued that God has the power to fill the [[vacuum]] with an infinite number of universes.<ref>{{citation|title=al-Razi, Fakhr al-Din (1149-1209)|work=[[Routledge Encyclopedia of Philosophy]]|author=John Cooper|year=1998|publisher=[[Routledge]]|url=http://www.muslimphilosophy.com/ip/rep/H044.htm|accessdate=2010-03-07}}</ref>
 
 
Al-Razi also argues that each of these universes may have its own possible "natural order" or physical laws. That other natural orders are possible, he argues, points to a willing maker who chooses one of many possibilities. [http://books.google.co.uk/books?id=97l0L7zKagkC]
 
 
====Observational astronomy====
 
{{see|Ulugh Beg Observatory|Zij-i Sultani}}
 
 
The [[transit of Venus]] and [[transit of Mercury]] were first observed by medieval Islamic astronomers. In the 11th century, the Persian polymath [[Avicenna]] observed the Venus transit of the Sun, when it was seen as a mark on its face. This helped him establish that Venus was, at least sometimes, below the Sun.<ref>{{citation|title=Ibn Sīnā: Abū ʿAlī al‐Ḥusayn ibn ʿAbdallāh ibn Sīnā|author=Sally P. Ragep|editor=Thomas Hockey|encyclopedia=The Biographical Encyclopedia of Astronomers|publisher=[[Springer Science+Business Media]]|year=2007|pages=570–572}}</ref> In the 12th century, the [[Al-Andalus|Andalusian]] astronomer [[Ibn Bajjah]] had observed them as "the two planets as black spots on the face of the Sun," evidently due to the transit of Venus and/or Mercury. In the 13th century, the [[Maragheh observatory|Maragha]] astronomer [[Qotb al-Din Shirazi]] referred to Ibn Bajjah's observation and identified it as the transit of Venus and Mercury.<ref>{{citation|title=History of oriental astronomy: proceedings of the joint discussion-17 at the 23rd General Assembly of the International Astronomical Union, organised by the Commission 41 (History of Astronomy), held in Kyoto, August 25–26, 1997|author=S. M. Razaullah Ansari|publisher=[[Springer Science+Business Media|Springer]]|year=2002|isbn=1402006578|page=137}}</ref>
 
 
The astronomical tradition established by the Maragha school continued at the [[Ulugh Beg Observatory]] at [[Samarkand]], in modern-day [[Uzbekistan]]. Founded by [[Ulugh Beg]] in the early 15th century, the observatory made considerable progress in observational astronomy. In the ''[[Zij-i Sultani]]'', Beg determined the length of the [[sidereal year]] as 365<sup>d</sup> 5<sup>h</sup> 49<sup>m</sup> 15<sup>s</sup>, which has an error of +25<sup>s</sup>, making it more accurate than [[Nicolaus Copernicus]]' estimate which had an error of +30<sup>s</sup>. Beg also determined the Earth's [[axial tilt]] as 23.52 degrees, which remains the most accurate measurement to date. It was more accurate than later measurements by Copernicus and [[Tycho Brahe]], and matches the currently accepted value precisely.<ref name=Thurston>Hugh Thurston, ''Early Astronomy'', (New York: Springer-Verlag), p. 194, ISBN 0-387-94107-X.</ref>
 
 
====Islamic astronomy in the Far East====
 
{{See also|Chinese astronomy|Islam in China|Islam in Korea}}
 
 
Muslim astronomers were brought to [[China]] in order to work on calendar making and astronomy during the [[Mongol Empire]] and the succeeding [[Yuan Dynasty]].<ref name=theearth/><ref name=Rufus/><ref>{{citation|contribution=Islamic and Chinese Astronomy under the Mongols: a Little-Known Case of Transmission|author=Benno van Dalen|title=From China to Paris: 2000 years transmission of mathematical ideas|editor=Yvonne Dold-Samplonius|publisher=Franz Steiner Verlag|year=2002|isbn=3515082239}}</ref> The Chinese scholar [[Yelü Chucai|Yeh-lu Chu'tsai]] accompanied [[Genghis Khan]] to Persia in 1210 and studied their calender for use in the Mongol Empire.<ref name=Rufus>{{citation|title=The Influence of Islamic Astronomy in Europe and the Far East|last=Rufus|first=W. C.|journal=Popular Astronomy|volume=47|issue=5|date=May 1939|pages=233–238 [237]}}</ref> [[Kublai Khan]] brought Iranians to [[Beijing Ancient Observatory|Beijing to construct an observatory]] and an institution for astronomical studies.<ref name=theearth>Richard Bulliet, Pamela Crossley, Daniel Headrick, Steven Hirsch, Lyman Johnson, and David Northrup. ''The Earth and Its Peoples''. 3. Boston: Houghton Mifflin Company, 2005. ISBN 0-618-42770-8</ref>
 
 
Several Chinese astronomers worked at the [[Maragheh observatory]], founded by [[Nasir al-Din al-Tusi]] in 1259 under the patronage of [[Hulagu Khan]] in Persia.<ref name=Walle>{{citation|title=The history of the relations between the Low Countries and China in the Qing era (1644-1911)|author=Willy vande Walle & Noël Golvers|publisher=[[Leuven University Press]]|year=2003|isbn=9058673154|page=38}}</ref> One of these Chinese astronomers was Fu Mengchi, or Fu Mezhai.<ref name=Dalen-19>{{citation|last=van Dalen|first=Benno|contribution=Islamic Astronomical Tables in China: The Sources for Huihui li|editor-last=Ansari|editor-first=S. M. Razaullah|year=2002|title=History of Oriental Astronomy|publisher=[[Springer Science+Business Media]]|isbn=1402006578|pages=19–32 [19]}}</ref> In 1267, the Persian astronomer [[Jamal ad-Din (astronomer)|Jamal ad-Din]], who previously worked at Maragha observatory, presented Kublai Khan with seven [[#Instruments|Persian astronomical instruments]], including a terrestrial [[globe]] and an [[armillary sphere]],<ref>{{cite book | last = Zhu | first = Siben | coauthors = Walter Fuchs | title = The "Mongol Atlas" of China | year = 1946 | publisher = [[Fu Jen Catholic University]] | location = [[Taipei]]}}</ref> as well as an astronomical [[almanac]], which was later known in China as the ''Wannian Li'' ("Ten Thousand Year Calender" or "Eternal Calendar"). He was known as "Zhamaluding" in China, where in 1271,<ref name=Dalen-19/> he was appointed by Khan as the first director of the Islamic observatory in Beijing,<ref name=Walle/> known as the Islamic Astronomical Bureau, which operated alongside the Chinese Astronomical Bureau for four centuries. Islamic astronomy gained a good reputation in China for its theory of planetary [[latitude]]s, which did not exist in Chinese astronomy at the time, and for its accurate prediction of eclipses.<ref name=Dalen-19/> Islamic astronomy also introduced the concept of a spherical Earth to Chinese astronomy, which previously believed the Earth to be flat. [http://scholar.google.co.uk/scholar?q=%22The+Chinese+first+encountered+the+image+of+a+spherical+earth+in+the+Yuan+dynasty%22]
 
 
Some of the astronomical instruments constructed by the famous Chinese astronomer [[Guo Shoujing]] shortly afterwards resemble the style of instrumentation built at Maragheh.<ref name=Walle/> In particular, the "simplified instrument" (''jianyi'') and the large [[gnomon]] at the [[Gaocheng Astronomical Observatory]] show traces of Islamic influence.<ref name=Dalen-20>{{citation|last=van Dalen|first=Benno|contribution=Islamic Astronomical Tables in China: The Sources for Huihui li|editor-last=Ansari|editor-first=S. M. Razaullah|year=2002|title=History of Oriental Astronomy|publisher=[[Springer Science+Business Media]]|isbn=1402006578|pages=19–32 [20]}}</ref> While formulating the [[Chinese calendar|Shoushili calendar]] in 1281, Shoujing's work in [[spherical trigonometry]] may have also been partially influenced by [[Mathematics in medieval Islam|Islamic mathematics]], which was largely accepted at Kublai's court.<ref name="ho 105">Ho, Peng Yoke. (2000). ''Li, Qi, and Shu: An Introduction to Science and Civilization in China'', p. 105. Mineola: Dover Publications. ISBN 0-486-41445-0.</ref> These possible influences include a pseudo-geometrical method for converting between [[equator]]ial and [[Ecliptic coordinate system|ecliptic coordinates]], the systematic use of [[decimal]]s in the underlying parameters, and the application of [[cubic interpolation]] in the calculation of the irregularity in the planetary motions.<ref name=Dalen-20/>
 
 
Around 1384 during the [[Ming Dynasty]], Emperor [[Hongwu Emperor|Zhu Yuanzhang]] ordered the [[Chinese language|Chinese]] translation and compilation of [[Zij|Islamic astronomical tables]], a task that was carried out by the scholars Mashayihei, a Muslim astronomer, and Wu Bozong, a Chinese scholar-official. These tables came to be known as the ''[[Hui people|Huihui]] Lifa'' (“''Muslim System of Calendrical Astronomy''”), which was published in China a number of times until the early 18th century,<ref>{{citation|title=The Korean Adaptation of the Chinese-Islamic Astronomical Tables|author=Yunli Shi|journal=Archive for History of Exact Sciences|publisher=[[Springer Science+Business Media|Springer]]|issn=1432-0657|volume=57|issue=1|date=January 2003|doi=10.1007/s00407-002-0060-z|pages=25–60 [26]}}</ref> though the [[Qing Dynasty]] had officially abandoned the tradition of Chinese-Islamic astronomy in 1659.<ref name=Shi-30/> A [[Korean language|Korean]] translation of the ''Huihui Lifa'' was also studied in [[Korea]] under the [[Joseon Dynasty]] during the time of [[Sejong the Great]] in the 15th century.<ref>{{citation|title=The Korean Adaptation of the Chinese-Islamic Astronomical Tables|author=Yunli Shi|journal=Archive for History of Exact Sciences|publisher=[[Springer Science+Business Media|Springer]]|issn=1432-0657|volume=57|issue=1|date=January 2003|doi=10.1007/s00407-002-0060-z|pages=25–60 [26–7]}}</ref> The tradition of Chinese-Islamic astronomy survived in Korea for even longer, up until the early 19th century.<ref name=Shi-30>{{citation|title=The Korean Adaptation of the Chinese-Islamic Astronomical Tables|author=Yunli Shi|journal=Archive for History of Exact Sciences|publisher=[[Springer Science+Business Media|Springer]]|issn=1432-0657|volume=57|issue=1|date=January 2003|doi=10.1007/s00407-002-0060-z|pages=25–60 [30]}}</ref>
 
 
====Islamic astronomy in Christian Europe====
 
[[File:Astrolabe quadrant England 1388.jpg|thumb|right|[[Astrolabe|Astrolabic]] [[Quadrant (astronomy)|quadrant]], England, 1388.]]
 
{{See also|Islamic contributions to Medieval Europe|Latin translations of the 12th century}}
 
 
During this period, [[Islam in Europe|Islamic-ruled regions of Europe]], such as [[Al-Andalus]], the [[Emirate of Sicily]], and [[History of Islam in southern Italy|southern Italy]], were slowly being reconquered by Christians. This led to the [[Latin translations of the 12th century|Arabic-Latin translation movement]], which saw the assimilation of [[Islamic contributions to Medieval Europe|knowledge from the Islamic world]] by [[Science in Medieval Western Europe|Western European science]], including astronomy.<ref name=Saliba/>
 
 
One of the most productive translators in Spain was [[Gerard of Cremona]], who translated 87 books from Arabic to Latin. The astronomical texts he translated include [[Jabir ibn Aflah]]'s ''Elementa astronomica'',<ref name=Katz>V. J. Katz, ''A History of Mathematics: An Introduction'', p. 291.</ref> [[Ahmad ibn Muhammad ibn Kathīr al-Farghānī]]'s ''On Elements of Astronomy on the Celestial Motions'',<ref>For a list of Gerard of Cremona's translations see: Edward Grant (1974) ''A Source Book in Medieval Science'', (Cambridge: Harvard Univ. Pr.), pp. 35-8 or Charles Burnett, "The Coherence of the Arabic-Latin Translation Program in Toledo in the Twelfth Century," ''Science in Context'', 14 (2001): at 249-288, at pp. 275-281.</ref> the works of [[Thabit ibn Qurra]] and [[Hunayn ibn Ishaq]],<ref>D. Campbell, ''Arabian Medicine and Its Influence on the Middle Ages'', p. 6.</ref> and the works of [[Arzachel]], the [[Banū Mūsā]] brothers, [[Abū Kāmil Shujā ibn Aslam]], [[Abu al-Qasim]], and [[Ibn al-Haytham]] (including the ''[[Book of Optics]]'').<ref name=Zaimeche/> The astronomical works translated by [[Plato Tiburtinus|Plato of Tivoli]] included [[Muhammad ibn Jābir al-Harrānī al-Battānī|Al-Battani]]'s astronomical and trigonometrical work ''De motu stellarum''. [[Muhammad ibn Mūsā al-Khwārizmī|Al-Khwarizmi]]'s ''Astronomical tables'' (also containing trigonometric tables) were translated by Robert of Chester<ref name=Katz/> and by [[Adelard of Bath]] (fl. 1116-1142), who also translated the ''Introduction to Astrology'' of [[Abu Mashar|Abū Ma'shar]].<ref>Charles Burnett, ed. ''Adelard of Bath, Conversations with His Nephew,'' (Cambridge: Cambridge University Press, 1999), p. xi.</ref> Adelard associated with other scholars in Western England such as [[Petrus Alphonsi|Peter Alfonsi]] and [[Walcher of Malvern]] who translated and developed the astronomical concepts brought from Islamic Spain.<ref>M.-T. d'Alverny, "Translations and Translators," pp. 440-3</ref> Other Arabic astronomical texts translated into Latin include [[Muhammad al-Fazari]]'s ''Great Sindhind'' (based on the ''[[Surya Siddhanta]]'' and the works of [[Brahmagupta]]).<ref>G. G. Joseph, ''The Crest of the Peacock'', p. 306</ref>
 
 
In addition to the Arabic-Latin translation movement in Western Europe, [[Byzantine science|Byzantine astronomers]] also translated Arabic texts on astronomy into [[Medieval Greek]] during this time. In particular, [[Gregory Choniades]], who had visited the famous [[Maragheh observatory]], translated various Arabic books on astronomy, including for example the works of Abu Ma'shar, [[Ibn Yunus]], [[Al-Khazini]] (who was of Byzantine Greek descent but raised in a Persian culture),<ref name=Pingree>[[David Pingree]] (1964), "Gregory Chioniades and Palaeologan Astronomy", ''Dumbarton Oaks Papers'' '''18''': 135-60</ref> Al-Khwārizmī<ref>{{citation|title=Reviews: ''The Astronomical Works of Gregory Chioniades, Volume I: The Zij al- Ala'i'' by Gregory Chioniades, David Pingree; ''An Eleventh-Century Manual of Arabo-Byzantine Astronomy'' by Alexander Jones|first=David A.|last=King|journal=[[Isis (journal)|Isis]]|volume=82|issue=1|date=March 1991|pages=116–8|doi=10.1086/355661}}</ref> and [[Nasīr al-Dīn al-Tūsī]] (such as the ''[[Zij-i Ilkhani]]'' and other [[Zij]] treatises) among others.<ref name="Leichter"/> Byzantine science thus played an important role in transmitting Arabic knowledge to Western Europe in later centuries, such as the transmission of the [[Tusi-couple]], which later appeared in the work of [[Nicolaus Copernicus]].<ref name=Leichter>{{cite web|author=Joseph Leichter|title=The Zij as-Sanjari of Gregory Chioniades|publisher=[[Internet Archive]]|date=June 27, 2009|year=2009|url=http://www.archive.org/details/TheZijAs-sanjariOfGregoryChioniades|accessdate=2009-10-02}}</ref><ref name=Saliba>{{cite web|author=[[George Saliba]]|title=Islamic Science and the Making of Renaissance Europe|date=2006-04-27|url=http://www.loc.gov/today/cyberlc/feature_wdesc.php?rec=3883|accessdate=2008-03-01}}</ref>
 
 
''[[De sphaera mundi]]'' was a [[medieval]] introduction to the basic elements of [[astronomy]] written by [[Johannes de Sacrobosco]] (John of Holywood) {{circa}} 1230. Based heavily on [[Ptolemy]]'s ''[[Almagest]]'' and Islamic astronomy, it was one of the most influential works of pre-[[Copernican Revolution|Copernican]] astronomy in Europe. For the task of predicting planetary motions they turned to the ''[[Alfonsine Tables]]'', a set of astronomical tables based on the ''Almagest'' models along with Islamic modifications, including the [[trepidation]] of [[Thabit ibn Qurra]].
 
 
===1450-1900===
 
This period was considered the period of stagnation, when the traditional system of astronomy continued to be practised with enthusiasm, but with decreasing innovation.<ref name=Dallal162/> It was believed there was no innovation of major significance during this period, but this view has been rejected by historians of astronomy in recent times, who argue that Muslim astronomers continued to make significant advances in astronomy through to the 16th century and possibly after this as well.<ref name=Ragep2/><ref name=Saliba-2000>{{Harv|Saliba|2000}}</ref> After the 16th century, there appears to have been little concern for [[Astrophysics|theoretical astronomy]], but [[observational astronomy]] in the Islamic tradition continued in the three Muslim [[Gunpowder warfare|gunpowder empires]]: the [[Ottoman Empire]], the [[Safavid dynasty]] of Persia, and the [[Mughal Empire]] of India.
 
 
====Astronomical physics and Earth's motion====
 
{{see also|Islamic cosmology}}
 
[[Image:Ali Kuşçu Portre.jpg|right|thumb|[[Ali Kuşçu|Ali al-Qushji]] provided [[Empirical research|empirical evidence]] for the [[Earth's rotation|Earth's motion]] and developed an [[Astrophysics|astronomical physics]] independent from [[Aristotelian physics]] and [[natural philosophy]].]]
 
 
The work of [[Ali Kuşçu|Ali al-Qushji]] (d. 1474), who worked at [[Samarkand]] and then [[Istanbul]], is seen as a late example of innovation in Islamic theoretical astronomy and it is believed he may have possibly had some influence on [[Nicolaus Copernicus]] due to similar arguments concerning the [[Earth's rotation]]. Before al-Qushji, the only astronomer to present [[Empirical research|empirical evidence]] for the Earth's rotation was [[Nasīr al-Dīn al-Tūsī]] (d. 1274), who used the phenomena of [[comet]]s to refute [[Ptolemy]]'s claim that a stationery Earth can be determined through observation. Al-Tusi, however, eventually accepted that the Earth was stationery on the basis of [[On the Heavens|Aristotelian cosmology]] and [[natural philosophy]]. By the 15th century, the influence of [[Aristotelian physics]] and natural philosophy was declining due to religious opposition from [[Islamic theology|Islamic theologians]] such as [[Al-Ghazali]] who opposed to the interference of [[Aristotelianism]] in astronomy, opening up possibilities for an astronomy unrestrained by philosophy. Under this influence, Al-Qushji, in his ''Concerning the Supposed Dependence of Astronomy upon Philosophy'', rejected Aristotelian physics and completely separated natural philosophy from astronomy, allowing astronomy to become a purely [[empirical]] and mathematical science. This allowed him to explore alternatives to the Aristotelian notion of a stationery Earth, as he explored the idea of a moving Earth. He also observed comets and elaborated on al-Tusi's argument. He took it a step further and concluded, on the basis of empirical evidence rather than speculative philosophy, that the moving Earth theory is just as likely to be true as the stationary Earth theory and that it is not possible to empirically deduce which theory is true.<ref name=Ragep/><ref name=Ragep2/><ref>Edith Dudley Sylla, "Creation and nature", in Arthur Stephen McGrade (2003), pp. 178-179, [[Cambridge University Press]], ISBN 0521000637.</ref>
 
 
His predecessor al-Tusi had previously realized that "the monoformity of falling bodies, and the uniformity of celestial motions," both moved “in a single way,” though he still relied on Aristotelian philosophy to provide "certain principles that only the natural philosophers could provide the astronomer." Qushji took this concept further and proposed that "the astronomer had no need for Aristotelian physics and in fact should establish his own physical principles independently of the natural philosophers." Alongside his rejection of Aristotle's concept of a stationary Earth,<ref>{{citation|first=F. Jamil|last=Ragep|title=Copernicus and his Islamic Predecessors: Some Historical Remarks|journal=Filozofski vestnik|volume=XXV|issue=2|year=2004|pages=125–142 [138-9]}}</ref> Qushji also rejected the Aristotelian notion of the heavenly bodies moving in [[uniform circular motion]].<ref name=Savage-Smith-541>{{citation|title=Islamic Influence on Copernicus|author=Emilie Savage-Smith|journal=Journal for the History of Astronomy|volume=39|issue=137|date=November 2008|pages=538-541 [541]|url=http://www.shpltd.co.uk/Journal%20for%20the%20History%20of%20Astronomy%20November.pdf|accessdate=2010-03-25}}</ref> His work was an important step away from Aristotelian physics and towards an independent [[Astrophysics|astronomical physics]].<ref>{{citation|first=F. Jamil|last=Ragep|title=Copernicus and his Islamic Predecessors: Some Historical Remarks|journal=Filozofski vestnik|volume=XXV|issue=2|year=2004|pages=125–142 [139]}}</ref> This is considered to be a "conceptual revolution"<ref name=Ragep-139>{{citation|first=F. Jamil|last=Ragep|title=Copernicus and his Islamic Predecessors: Some Historical Remarks|journal=Filozofski vestnik|volume=XXV|issue=2|year=2004|pages=125–142 [139]}}</ref><ref name=Savage-Smith-2008>{{citation|title=Islamic Influence on Copernicus|author=Emilie Savage-Smith|journal=Journal for the History of Astronomy|volume=39|issue=4|date=November 2008|pages=538-541 [541]|url=http://www.shpltd.co.uk/Journal%20for%20the%20History%20of%20Astronomy%20November.pdf|accessdate=2010-03-25}}</ref> that had no precedent in European astronomy prior to the [[Copernican Revolution]] in the 16th century.<ref>{{citation|title=Copernicus and His Islamic Predecessors: Some Historical Remarks|author=F. Jamil Ragep|journal=Filozofski vestnik|volume=XXV|issue=2|year=2004|pages=125–142 [139]|quote=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. 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.}}</ref> Despite the similarity in their discussions regarding the Earth's motion, there is uncertainty over whether al-Qushji had any influence on Copernicus. However, it is likely that they both may have arrived at similar conclusions due to using the earlier work of al-Tusi as a basis. This is more of a possibility considering "the remarkable coincidence between a passage in ''De revolutionibus'' (I.8) and one in Ṭūsī’s ''Tadhkira'' (II.1[6]) in which Copernicus follows Ṭūsī’s objection to Ptolemy’s “proofs” of the Earth’s immobility." This can be considered as evidence that not only was Copernicus influenced by the mathematical models of Islamic astronomers, but may have also been influenced by the astronomical physics they began developing and their views on the Earth's motion.<ref>{{citation|first=F. Jamil|last=Ragep|title=Copernicus and his Islamic Predecessors: Some Historical Remarks|journal=Filozofski vestnik|volume=XXV|issue=2|year=2004|pages=125–142 [137–9]}}</ref>
 
 
In the early 16th century, the debate on the Earth's motion was continued by [[Al-Birjandi]] (d. 1528), who in his analysis of what might occur if the Earth were moving, develops a hypothesis similar to [[Galileo Galilei]]'s notion of "circular [[inertia]]",<ref>{{Harv|Ragep|2001b|pp=63-4}}</ref> which he described in the following observational test (as a response to one of [[Qutb al-Din al-Shirazi]]'s arguments):
 
 
{{quote|"The small or large rock will fall to the Earth along the path of a line that is perpendicular to the plane (''sath'') of the horizon; this is witnessed by experience (''tajriba''). And this perpendicular is away from the tangent point of the Earth’s sphere and the plane of the perceived (''hissi'') horizon. This point moves with the motion of the Earth and thus there will be no difference in place of fall of the two rocks."<ref>{{Harv|Ragep|2001a|pp=152-3}}</ref>}}
 
 
[[Bahāʾ al-dīn al-ʿĀmilī]] (18 February 1547 - 1 September 1621), the leading astronomer of [[Safavid dynasty|Safavid Persia]], wrote the ''Tashrīḥ al‐aflāk'' (''Anatomy of the celestial spheres''), a summary of theoretical astronomy where he affirms the view that supports the positional rotation of the Earth. He advocated the feasibility of the Earth's rotation in the 16th century, independent of any Western influences (and prior to the spread of Copernican theories). Baha al-Din pointed out that no sufficient proof has been offered so far to the contrary.<ref>{{cite encyclopedia | editor = Thomas Hockey et al | last = Hashemipour | first = Behnaz | title=ʿĀmilī: Bahāʾ al‐Dīn Muḥammad ibn Ḥusayn al‐ʿĀmilī | encyclopedia = The Biographical Encyclopedia of Astronomers | publisher = Springer | year = 2007 | location = New York | pages = 42–3 | url=http://islamsci.mcgill.ca/RASI/BEA/Amili_BEA.htm | isbn=978-0-387-31022-0| ref=harv}} ([http://islamsci.mcgill.ca/RASI/BEA/Amili_BEA.pdf PDF version])</ref>
 
 
====Planetary theory====
 
It was traditionally believed that Islamic astronomers made no more advances in planetary theory after the work of [[Ibn al-Shatir]] in the 14th century, but recent studies have shown that there were several significant advances in planetary theory through to the 16th century. [[Ali Qushji]], for example, improved on al-Tusi's planetary model and presented an alternative planetary model for [[Mercury (planet)|Mercury]].<ref>{{citation|last=Saliba|first=George|author-link=George Saliba|title=Arabic planetary theories after the eleventh century AD|pages=123–4}}, in {{Harv|Rashed|Morelon|1996|pp=58-127}}</ref> He also rejected the Aristotelian notion of the planets moving in [[uniform circular motion]].<ref name=Savage-Smith-541/>
 
 
According Robert Morrison, Qushji's work is "relevant for understanding Copernicus’s transformation of a geocentric system into a heliocentric one." According to F. Jamil Ragep, "the mathematical accuracy of Copernicus’s heliocentric system would have been unattainable without the mathematical transformation enabled by Qushjı’s demonstration of the equivalence of the epicyclic and eccentric hypotheses for retrograde motion." Morrison also writes that Qushji's "proof of the possibility of transformation of epicyclic models to eccentric models in the models of the lower planets has been recognized by Owen Gingerich as relevant to the history of the heliocentric arrangement." [http://www.bowdoin.edu/faculty/r/rgmorris/pdf/scholarly-intermediary-2014.pdf]
 
 
[[George Saliba]] also studied the works of a 16th century astronomer, [[Shams al-Din al-Khafri]] (d. 1550), a [[Safavid]] Persian commentator on earlier [[Maragheh observatory|Maragha astronomers]]. Saliba wrote the following on al-Khafri's work:
 
 
{{quote|By his sheer insight into the role of mathematics in describing natural phenomena, this astronomer managed to bring the hay'a tradition to such unparalleled heights that could not be matched anywhere else in the world at that time neither mathematically nor astronomically. By working on the alternative mathematical models that could replace those of Ptolemy, and by scrutinizing the works of his predecessors who were all searching for unique mathematical models that could describe the physical phenomena consistently, this astronomer finally realized that all mathematical modeling had no physical truth by itself and was simply another language with which one could describe the physical observed reality. He also realized that the specific phenomena that were being described by the Ptolemaic models did not have unique mathematical solutions that were subject to the same restraints. Rather there were several mathematical models that could account for the Ptolemaic observations, yield identical predictive results at the same critical points used by Ptolemy to construct his own models (thus accounting for the observations as perfectly as Ptolemy could) and still meet the consistency requirement that was imposed by the Aristotelian cosmology which was adopted by the writers in the ''hay'a'' tradition.<ref name=Saliba-2000/>}}
 
 
[[Image:Heliocentric.jpg|thumb|right|A model of the [[Copernican heliocentrism|heliocentric system]] attributed to [[Nicolaus Copernicus]].]]
 
 
====Ottoman observational astronomy====
 
{{see also|Science and technology in the Ottoman Empire}}
 
 
Another notable 16th century Muslim astronomer was the [[Ottoman Empire|Ottoman]] astronomer [[Taqi al-Din Muhammad ibn Ma'ruf|Taqi al-Din]], who built the [[Istanbul observatory of Taqi al-Din]] in 1577, where he carried out astronomical observations until 1580. He produced a [[Zij]] (named ''Unbored Pearl'') and [[astronomical catalog]]ues that were more accurate than those of his contemporaries, [[Tycho Brahe]] and [[Nicolaus Copernicus]]. Taqi al-Din was also the first astronomer to employ a [[Decimal separator|decimal point]] notation in his [[observation]]s rather than the [[sexagesimal]] fractions used by his contemporaries and predecessors.<ref name=Tekeli>Sevim Tekeli, "Taqi al-Din", in Helaine Selin (1997), ''Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures'', [[Kluwer Academic Publishers]], ISBN 0792340663.</ref> He also invented a variety of astronomical instruments, including accurate mechanical [[astronomical clock]]s from 1556 to 1580.
 
 
Earlier in 1574, Taqi al-Din used [[astrophysics]] to explain the intromission model of vision. He stated since the [[star]]s are millions of kilometers away from the [[Earth]] and that the [[speed of light]] is constant, that if light had come from the eye, it would take too long for light "to travel to the star and come back to the eye. But this is not the case, since we see the star as soon as we open our eyes. Therefore the light must emerge from the object not from the eyes."<ref name=Topdemir>{{citation|first=Hüseyin Gazi|last=Topdemir|title=Takîyüddîn'in Optik Kitabi|publisher=Ministry of Culture Press, [[Ankara]]|year=1999}} ([[cf.]] {{cite web|author=Dr. Hüseyin Gazi Topdemir|title=Taqi al-Din ibn Ma‘ruf and the Science of Optics: The Nature of Light and the Mechanism of Vision|publisher=FSTC Limited|url=http://muslimheritage.com/topics/default.cfm?ArticleID=951|date=30 June 2008|accessdate=2008-07-04}})</ref>
 
 
After the destruction of the Istanbul observatory of Taqi al-Din in 1580, astronomical activity stagnated in the Ottoman Empire, until the introduction of [[Copernican heliocentrism]] in 1660, when the Ottoman scholar Ibrahim Efendi al-Zigetvari Tezkireci translated Noël Duret's French astronomical work (written in 1637) into Arabic.<ref>{{citation|last=Zaken|first=Avner Ben|year=2004|title=The heavens of the sky and the heavens of the heart: the Ottoman cultural context for the introduction of post-Copernican astronomy|journal=The British Journal for the History of Science|publisher=[[Cambridge University Press]]|volume=37|pages=1–28}}</ref>
 
 
====Islamic astronomy in India====
 
{{See also|Indian astronomy|Islam in India}}
 
 
In the [[Mughal Empire]], the 16th and 17th centuries saw a synthesis between Islamic and [[Indian astronomy]], where Islamic observational techniques and instruments were combined with [[Indian mathematics|Hindu computational]] techniques. While there appears to have been little concern for theoretical astronomy, Muslim and [[Hindu]] astronomers in [[History of India|India]] continued to make advances in [[observational astronomy]] and produced nearly a hundred ''[[Zij]]'' treatises. [[Humayun]] built a personal observatory near [[Delhi]], while [[Jahangir]] and [[Shah Jahan]] were also intending to build observatories but were unable to do so. After the decline of the Mughal Empire, however, it was a Hindu king, [[Jai Singh II of Amber]], who attempted to revive the Islamic tradition of astronomy in India. In the early 18th century, he built several large observatories called [[Yantra Mandir]]s in order to rival the famous Samarkand observatory, and in order to update [[Ulugh Beg]]'s ''[[Zij-i-Sultani]]'' with more accurate observations. The instruments and observational techniques used at the observatory were mainly derived from the Islamic tradition, and the computational techniques from the Hindu tradition.<ref name=Sharma>{{citation|title=Sawai Jai Singh and His Astronomy|first=Virendra Nath|last=Sharma|year=1995|publisher=[[Motilal Banarsidass]] Publ.|isbn=8120812565|pages=8–9}}</ref><ref name=Baber>{{citation |title=The Science of Empire: Scientific Knowledge, Civilization, and Colonial Rule in India |first=Zaheer |last=Baber |year=1996 |publisher=[[State University of New York Press]] |isbn=0791429199 |pages=82–9 |ref=}}</ref> In particular, one of the most remarkable astronomical instruments invented by Muslims in Mughal India is the seamless celestial globe (see [[#Globes|Globes]] below).
 
 
Jai Singh also invited European [[Jesuit]] astronomers to his observatory, who had bought back the astronomical tables compiled by [[Philippe de La Hire]] in 1702. After examining La Hire's work, Jai Singh concluded that the techniques and instruments used in the European tradition were inferior to the Islamic and Indian traditions. It is uncertain whether Islamic astronomers in India were aware of the [[Copernican Revolution]] via the Jesuits, but it appears they were not concerned with theoretical astronomy, hence the theoretical advances in Europe did not interest them at the time.<ref>{{citation |title=The Science of Empire: Scientific Knowledge, Civilization, and Colonial Rule in India |first=Zaheer |last=Baber |year=1996 |publisher=[[State University of New York Press]] |isbn=0791429199 |pages=89–90 |ref=}}</ref> They did, however, employ the use of [[telescope]]s. In the ''Zij-i Muhammad Shahi'', Jai Singh states: "telescopes were constructed in my kingdom and using them a number of observations were carried out."<ref name=Ansari>{{citation|title=History of oriental astronomy: proceedings of the joint discussion-17 at the 23rd General Assembly of the International Astronomical Union, organised by the Commission 41 (History of Astronomy), held in Kyoto, August 25–26, 1997|author=S. M. Razaullah Ansari|publisher=[[Springer Science+Business Media|Springer]]|year=2002|isbn=1402006578|page=141}}</ref>
 
 
Following the arrival of the British [[East India Company]] in the 18th century, Islamic astronomy was slowly displaced by European astronomy, though there were attempts at harmonizing the two traditions. For example, the Indian Islamic scholar Mir Muhammad Hussain had travelled to England in 1774 to study Western science and, on his return to India in 1777, he wrote a Persian treatise on astronomy. He wrote about the [[Heliocentrism|heliocentric]] model, and argued that there exists an infinite number of [[universe]]s (''awalim''), each with their own planets and stars, and that this demonstrates the [[omnipotence]] of God, who is not confined to a single universe. Hussain's idea of a universe resembles the modern concept of a [[galaxy]], thus his view corresponds to the modern view that the universe consists of billions of galaxies, each one consisting of billions of stars.<ref>{{citation|title=History of oriental astronomy: proceedings of the joint discussion-17 at the 23rd General Assembly of the International Astronomical Union, organised by the Commission 41 (History of Astronomy), held in Kyoto, August 25–26, 1997|author=S. M. Razaullah Ansari|publisher=[[Springer Science+Business Media|Springer]]|year=2002|isbn=1402006578|pages=133–4}}</ref> The last known ''Zij'' treatise was the ''Zij-i Bahadurkhani'', written in 1838 by the Indian astronomer Ghulam Hussain Jaunpuri (1760–1862) and printed in 1855, dedicated to [[Bahadur Khan]]. The treatise incorporated the heliocentric system into the ''Zij'' tradition.<ref>{{citation|title=History of oriental astronomy: proceedings of the joint discussion-17 at the 23rd General Assembly of the International Astronomical Union, organised by the Commission 41 (History of Astronomy), held in Kyoto, August 25–26, 1997|author=S. M. Razaullah Ansari|publisher=[[Springer Science+Business Media|Springer]]|year=2002|isbn=1402006578|page=138}}</ref>
 
 
===1900-present===
 
In the 20th and 21st centuries, Islamic astronomers have been making advances in moon sighting, while [[astronaut]]s and [[Aerospace engineering|rocket scientist]]s from the Islamic world have been involved in research on [[astronautics]] and [[space exploration]].
 
 
====Astronautics and space exploration====
 
<!-- Deleted image removed: [[Image:Kerimov21.jpg|thumb|[[Kerim Kerimov]], one of the founders of the [[Soviet space program]].{{puic|1=Kerimov21.jpg|log=2009 August 10}}]] -->
 
 
[[Kerim Kerimov]] from [[Azerbaijan]] (then part of the [[Soviet Union]]) was one of the most important key figures in early space exploration. He was one of the founders of the [[Soviet space program]], one of the lead architects behind the first [[satellite]] ([[Sputnik 1]])<ref>{{citation|contribution=Kerim Kerimov|title=[[Encyclopædia Britannica]]|url=http://www.britannica.com/EBchecked/topic/914879/Kerim-Kerimov|accessdate=2008-10-12}}</ref> and first [[human spaceflight]] ([[Vostok 1]]), and responsible for the launch of the first [[space dock]]s (the [[Cosmos 186]] and [[Cosmos 188]]) and the first [[space station]]s (the [[Salyut]] and [[Mir]] series).<ref>{{citation|first=Peter|last=Bond
 
|url=http://findarticles.com/p/articles/mi_qn4158/is_20030407/ai_n12692130|contribution=Obituary: Lt-Gen Kerim Kerimov|title=[[The Independent]]|date=7 April 2003|accessdate=2008-01-22|archiveurl=http://archive.is/3j2Z4|archivedate=2008-12-17}}</ref><ref>{{citation|first=Betty|last=Blair|year=1995|title=Behind Soviet Aeronauts|journal=[[Azerbaijan International]]|volume=3|issue=3}}</ref>
 
 
[[Farouk El-Baz]] from [[Egypt]] worked for the rival [[NASA]] and was involved in the first [[Moon landing]]s with the [[Apollo program]], where he was secretary of the ''Landing Site Selection Committee'', ''Principal Investigator of Visual Observations and Photography'', chairman of the ''Astronaut Training Group'', and assisted in the planning of scientific explorations of the Moon, including the selection of landing sites for the Apollo missions and the training of astronauts in lunar observations and photography.<ref>{{cite web|url= http://www.islamonline.net/servlet/Satellite?c=Article_C&cid=1169545087624&pagename=Zone-English-HealthScience%2FHSELayout |title=Muslim Scientists and Space Exploration - Farouk El-Baz: With Apollo to the Moon - Interview|publisher=[[IslamOnline]]|accessdate=2008-01-15}}</ref>
 
 
In the late 20th and early 21st centuries, there have also been a number of astronauts from the Islamic world, the first being [[Sultan bin Salman bin Abdulaziz Al Saud]] as a [[Payload Specialist]] aboard [[STS-51-G]] [[Space Shuttle Discovery]], followed by [[Muhammed Faris]] aboard [[Soyuz TM-2]] and [[Soyuz TM-3]] to [[Mir]] [[space station]]; [[Abdul Ahad Mohmand]] aboard [[Soyuz TM-5]] to Mir; [[Talgat Musabayev]] (one of the [[Spaceflight records#Total time in space|top 25 astronauts by time in space]]) as a [[flight engineer]] aboard [[Soyuz TM-19]] to Mir, commander of [[Soyuz TM-27]] to Mir, and commander of [[Soyuz TM-32]] and [[Soyuz TM-31]] to [[International Space Station]] (ISS); and [[Anousheh Ansari]], the first woman to travel to ISS and the fourth [[space tourist]].
 
 
In 2007, [[Sheikh Muszaphar Shukor]] from [[Malaysia]] traveled to ISS with his [[Expedition 16]] crew aboard [[Soyuz TMA-11]] as part of the [[Angkasawan program]] during [[Ramadan]], for which the [[National Fatwa Council]] wrote ''Guidelines for Performing Islamic Rites ([[Ibadah]]) at the International Space Station'', giving advice on issues such as [[Salah|prayer]] in a low-gravity environment, the location of [[Mecca]] from ISS, determination of prayer times, and issues surrounding [[Sawm|fasting]]. Shukor also celebrated [[Eid ul-Fitr]] aboard ISS. He was both an astronaut and an [[orthopedic surgeon]], and is most notable for being the first to perform [[biomedical research]] in space, mainly related to the characteristics and growth of liver [[cancer]] and [[leukemia]] cells and the crystallization of various [[protein]]s and [[microbe]]s in space.<ref>{{Cite web|url=http://thestar.com.my/news/story.asp?file=/2007/10/11/nation/19136025&sec=nation|title=Mission in space|accessdate=October 13, 2007|publisher=[[The Star (Malaysia)|The Star]]|date=October 13, 2007|author=[[The Star (Malaysia)|The Star]]}}</ref>
 
 
Other prominent scientists from the Islamic world involved in research on the [[space science]]s and space exploration include Essam Heggy who is working in the NASA Mars Exploration Program in the Lunar and Planetary Institute in Houston, as well as Ahmed Salem, Alaa Ibrahim, Mohamed Sultan, and Ahmed Noor.<ref>{{cite web|url=
 
http://www.islamonline.net/servlet/Satellite?c=Article_C&cid=1177155965285&pagename=Zone-English-HealthScience%2FHSELayout |title=Muslim Scientists and Space Exploration - Essam Heggy: Into the Heart of Mars - Interview|publisher=[[IslamOnline]]|accessdate=2008-01-15}}</ref>
 
 
====New efforts in moon sighting====
 
According to Islam, Muslims should observe religious duties during special days on the basis of the [[Islamic calendar|Islamic lunar calendar]]. Therefore, moon sighting is an important issue for Muslims.<ref name="Moon sighting">{{citation|url=http://online.wsj.com/article_email/SB119239099536758507-lMyQjAxMDE3OTEyNTMxOTUwWj.html |title=Muslim Moon Hunting Evolves|author=Farnaz Fassihi|date=October 15, 2007|journal=[[The Wall Street Journal]]|page=A8|accessdate=2008-01-24}}</ref> In recent years, due to global communication and using modern technologies to see the [[new moon]], a new trend has formed among Muslims in this field<ref>{{cite web|url=http://moonsighting.com|title=Moon Sighting|accessdate=2008-01-24}}</ref><ref>{{cite web|url=http://www.hilal-sighting.com|title=Hilal-Sighting|publisher=[[Columbia University]], [[New York]]|accessdate=2008-01-24}}</ref><ref>{{cite web|url=http://www.icoproject.org|title=Islamic crescent's observation project|accessdate=2008-01-24}}</ref> and new [[Fiqh|religious]] questions have emerged.<ref>{{cite web|url=http://islam.about.com/od/ramadan/a/moonsighting.htm|title=Moon-Sighting at Ramadan|author=Huda|accessdate=2008-01-24}}</ref>
 
 
In 2005, [[Ayatollah]] [[Ali Khamenei]], [[Faqih|religious scholar]] and [[supreme leader]] of [[Iran]], issued a [[fatwa]] to use modern technologies for moon sighting. The [[Islamic Society of North America]] in Plainfield, Ind., followed suit last year. Muslims are scrambling for a technological edge in the annual moon-hunting ritual.<ref name="Moon sighting"/><ref>{{cite web|url= http://www.gulf-times.com/site/topics/article.asp?cu_no=2&item_no=109235&version=1&template_id=57&parent_id=56 |title=Fasting month of Ramadan begins in Qatar today|work=[[Gulf Times]]|date=23 September 2006|accessdate=2008-01-24}}</ref>
 
 
Ayatollah Khamenei has established a Moon Observation Committee, composed of [[cleric]]s who pore over sightings reported to centers. Scientists note the moon's angle, position, and illumination, and compare the sightings from the field with [[computer]]ized [[chart]]s that pinpoint where the moon should be. In Iran, groups of astronomers accompanied by a cleric are dispatched across the country, some using [[night vision]] gear lent by the [[military of Iran]] and high-definition telescopes from the [[List of universities in Iran|universities]]. Iran also sends up a chartered airplane with an astronomer aboard. The plane is loaded with sensitive observation and photographic equipment, along with a [[laptop]]. Iranian [[mapmaker]]s at the National Geography Organization in [[Tehran]] have created a three-dimensional map of the country identifying 70 locations where the new moon might best be seen.<ref name="Moon sighting"/> There are similar efforts in other [[Muslim countries]] as well.
 
 
There is also a competition among astronomers to see the younger moon with naked eyes. According to the Islamic lunar calendar in Iran, the new "World Record for Lunar Crescent Sighting" has been established on September 7, 2002 (Jamadi-al Thani 29, 1423 AH) by Mohsen Ghazi Mirsaeed on the north-west heights (2,110 meters ) of [[Zarand, Iran|Zarand]] in Rashk Bala village (31°, 04' N , 56°, 28' E). The record for the moon age at the moment of first visibility with naked eyes is 11 hours and 42 minutes.<ref>{{cite web|url=http://www.icoproject.org/icop/grecord.html|title=A New World Record for Lunar Crescent Sighting By Mr. Mohsen G. Mirsaeed|publisher=Islamic Crescents' Observation Project|accessdate=2008-01-24}}</ref>
 
 
==Observatories==
 
Islamic astronomers had based their work largely on actual observations of the heavens, far more so than earlier Greek astronomers who relied heavily upon abstract calculation.<ref>{{citation|title=The Astronomical Manuscripts of Naṣīr al-Dīn Ṭūsī|author=Ute Ballay|journal=[[Arabica (journal)|Arabica]]|volume=37|issue=3|date=November 1990|pages=389-392 [389]|publisher=[[Brill Publishers]]|url=http://www.jstor.org/stable/4057148|accessdate=2010-03-29}}</ref> This led to the emergence of the modern astronomical [[observatory]] as a [[research institute]]<ref name=Kennedy-1962/> (as opposed to a private [[observation post]] as was the case in ancient times)<ref name = "Micheau-992-3">{{citation|last=Micheau|first=Francoise|contribution=The Scientific Institutions in the Medieval Near East|pages=992–3}}, in {{Harv|Rashed|Morelon|1996|pp=985-1007}}</ref> being first introduced by medieval Muslim astronomers, who produced accurate [[Zij]] treatises using these observatories. The Islamic observatory was the first specialized astronomical institution with its own scientific staff,<ref name=Kennedy-1962/> [[Director (education)|director]], astronomical [[Program Management|program]],<ref name = "Micheau-992-3"/> large [[#Instruments|astronomical instruments]], and building where astronomical [[research]] and [[observation]]s are carried out. Islamic observatories were also the first to employ enormously large astronomical instruments in order to greatly improve the accuracy of their observations.<ref name=Kennedy-1962>{{Harv|Kennedy|1962}}</ref>
 
 
The medieval Islamic observatories were also the earliest institutions to emphasize group research (as opposed to individual research) and where "theoretical investigations went hand in hand with observations." In this sense, they were similar to modern scientific research institutions.<ref>{{citation|last=Prof. Bakar|first=Osman ([[Georgetown University]])|publisher=CIC's annual Ottawa dinner|url=http://www.al-huda.com/Article_5%205.htm|title=Islam's Contribution to Human Civilization: Science and Culture|date=October 15, 2001|accessdate=2008-01-22}}</ref>
 
 
===Early observatories===
 
The first systematic observations are reported to have taken place under the patronage of [[al-Ma'mun]], and the first Islamic observatories were built in 9th century [[Iraq]] under his patronage. In many private observatories from [[Damascus]] to [[Baghdad]], [[meridian (geography)|meridian]] degrees were measured, solar parameters were established, and detailed observations of the [[Sun]], [[Moon]], and [[planets]] were undertaken. One of these early observatories in Baghdad was the Al-Shammisiyyah observatory, where between 825 to 835, [[Habash al-Hasib al-Marwazi]] conducted various observations and estimated a number of geographic and astronomical values.<ref name=Langermann/> The observatory commissioned by Al-Mamun in Baghdad was the world's first state-funded, large-scale science project.<ref>Al-Khalili, Jim (2012), ''[http://books.google.co.uk/books?id=Jzb7u6Ty-hYC&printsec=frontcover Pathfinders: The Golden Age of Arabic Science]'', Penguin, ISBN 0141038365</ref>
 
 
In the 10th century, the [[Buwayhid]] dynasty encouraged the undertaking of extensive works in Astronomy, such as the construction of a large scale instrument with which observations were made in the year 950. We know of this by recordings made in the ''zij'' of astronomers such as Ibn al-Alam. The great astronomer [[Abd Al-Rahman Al Sufi]] was patronised by prince [['Adud al-Dawla]], who systematically revised [[Ptolemy]]'s catalogue of [[star]]s. [[Abu-Mahmud al-Khujandi]] also constructed an observatory in [[Ray, Iran|Ray]], Iran where he is known to have constructed the first huge [[sextant (astronomical)|mural sextant]] in 994 AD.<ref>{{MacTutor|id=Al-Khujandi|title=Abu Mahmud Hamid ibn al-Khidr Al-Khujandi}}</ref> [[Sharaf al-Daula]] also established a similar observatory in [[Baghdad]]. Reports by [[Ibn Yunus]] and [[al-Zarqall]] in [[Toledo, Spain|Toledo]] and [[Córdoba, Spain|Cordoba]] indicate the use of sophisticated instruments for their time.
 
 
It was [[Malik Shah I]] who established the first large observatory, probably in [[Isfahan (city)|Isfahan]]. It was here where [[Omar Khayyám]] with many other collaborators constructed a [[zij]] and formulated the [[Iranian calendar|Persian solar calendar]], a.k.a. the ''jalali calendar'', the most accurate [[solar calendar]] to date. A modern version of this calendar is still in official use in [[Iran]] today.
 
 
===Further development===
 
====Maragheh observatory====
 
{{Main|Maragheh observatory}}
 
[[Image:Maragheh Observatory.jpg|thumb|right|Current status of [[Maragheh observatory]].]]
 
 
The more influential observatories were established beginning in the 13th century. The [[Maragheh observatory]] was founded by [[Nasīr al-Dīn al-Tūsī]] under the patronage of [[Hulegu Khan]] in the 13th century. Here, al-Tusi supervised its technical construction at [[Maragheh]]. The facility contained resting quarters for [[Hulagu Khan]], as well as a library and mosque. Some of the top astronomers of the day gathered there, and their collaboration resulted in important alternatives to the [[Ptolemaic model]] over a period of 50 years. The observations of al-Tusi and his team of researchers were compiled in the ''[[Zij-i Ilkhani]]''.
 
 
====Ulugh Beg Observatory====
 
{{Main|Ulugh Beg Observatory}}
 
[[Image:Soviet Union stamp 1987 CPA 5876.jpg|thumb|left|[[Ulugh Beg]], founder of the large [[Ulugh Beg Observatory]] in [[Samarkand]], honored on this [[Soviet]] stamp.]]
 
 
In 1420, prince [[Ulugh Beg]], himself an astronomer and mathematician, founded another large observatory, the [[Ulugh Beg Observatory]], in [[Samarkand]]. The remains of the observatory were excavated in 1908 by Russian teams. Ulugh Beg, alongside his team of researchers that included [[Jamshīd al-Kāshī]] and [[Ali Qushji]], compiled the results of their observations in the ''[[Zij-i-Sultani]]'' (1437).
 
 
====Istanbul observatory of Taqi al-Din====
 
{{Main|Istanbul observatory of Taqi al-Din}}
 
[[File:Istambul observatory in 1577.jpg|thumb|[[Istanbul observatory of Taqi al-Din]] in 1577.]]
 
 
In 1577, [[Taqi al-Din Muhammad ibn Ma'ruf]] founded a large [[Istanbul observatory of Taqi al-Din|observatory in Istanbul]]. This was on the same scale as those in Maragha and Samarkand as well as that of his contemporary [[Tycho Brahe]]. In fact, the accuracy of Taqi al-Din's observations surpassed that of Tycho Brahe.
 
 
====Islamic observatories in India====
 
{{See also|Indian astronomy}}
 
 
In the [[Mughal Empire]], [[Humayun]] built a personal observatory near [[Delhi]] in the 16th century, while [[Jahangir]] and [[Shah Jahan]] were also intending to build observatories but were unable to do so. After the decline of the Mughal Empire, the Hindu king [[Jai Singh II of Amber]] built several large observatories called [[Yantra Mandir]]s inspired by the famous Samarkand observatory. The instruments and observational techniques used at the observatory were mainly derived from the Islamic tradition, and the computational techniques from the Hindu tradition.<ref name=Sharma/><ref name=Baber/>
 
 
===Modern observatories===
 
In modern times, many well-equipped observatories can be found in [[Jordan]],<ref>{{cite web|url=http://www.jas.org.jo/index2.html|title=Jordanian Astronomical Society|accessdate=2008-01-15}}</ref> [[Palestine]],<ref>{{cite web|url=http://www.pas.ps/maine.htm|title=Palestinian Astronomical Society|accessdate=2008-01-15}}</ref> [[Lebanon]],<ref>{{cite web|url=http://www.geocities.com/CapeCanaveral/Hall/6865|title=Lebanese Astronomical society|accessdate=2008-01-15|archiveurl=http://web.archive.org/20000902183234/www.geocities.com/CapeCanaveral/Hall/6865|archivedate=2000-09-02}}</ref> [[UAE]],<ref>{{cite web|url=http://www.falak.ae|title=Emirates Astronomical Society|accessdate=2008-01-15}}</ref> [[Tunisia]],<ref>{{cite web|url=http://www.satunisia.info/angstro.htm|title=Société Astronomique de Tunise|accessdate=2008-01-15}}</ref> and other Arab states are also active as well. [[Iran]] has modern facilities at [[Shiraz University]] and [[Tabriz University]]. In December 2005, ''[[Physics Today]]'' reported of Iranian plans to construct a "world class" facility with a 2.0 meter [[telescope]] observatory in the near future.<ref>{{cite web|author=Feder Toni|month=July | year=2004|url=http://www.physicstoday.org/vol-57/iss-7/p28a.html|title=Iran Invests in Astronomy|publisher=[[Physics Today]]|accessdate=2008-01-22}}</ref>
 
 
==Instruments==
 
{{See also|Inventions in the Muslim world}}
 
[[Image:Astrolabium.jpg|thumb|A [[Persia]]n ([[Iran]]ian) [[astrolabe]] from [[1208]].]]
 
 
Modern knowledge of the instruments used by Muslim astronomers primarily comes from two sources. First the remaining instruments in private and museum collections today, and second the treatises and manuscripts preserved from the Middle Ages.
 
 
Muslims both made many improvements to instruments already in use before their time, such as adding new scales or details and significantly enlarging them to improve accuracy,<ref name=Thurston/> and invented many of their own new instruments. Islamic astronomers were also the first to build enormously large scientific instruments in order to greatly improve the accuracy of observations.<ref name=Kennedy-1962/> Their contributions to astronomical instrumentation are abundant. Many of these instruments were often invented or designed for [[Islam]]ic purposes, such as the determination of the [[Qibla]] (direction to [[Mecca]]) or the [[Salat times|times of Salah]] prayers.
 
 
===Astrolabes and planisphere===
 
{{See also|Astrolabe}}
 
 
Brass [[astrolabe]]s were developed in much of the [[Islamic]] world, often as an aid to finding the [[qibla]]. The [http://www.soas.ac.uk/visitors/gallery/previous/islamicpatronage/popup25732.html earliest known example] is dated 315 [[Islamic calendar|AH]], (927/8 CE). The first person credited for building the Astrolabe in the Islamic world is reportedly [[Al-Fazari, Mohammad|Fazari]].<ref>[[Richard Nelson Frye]], ''Golden Age of Persia'', p. 163.</ref> Though the first astrolabe to chart the stars was invented in the [[Hellenistic civilization]], Fazari made several improvements to the device, such as the introduction of angular scales to the astrolabe,<ref>{{citation|title=Surveying and navigational instruments from the historical standpoint|author=L. C. Martin|year=1923|[[Optical Society of America|Transactions of the Optical Society]]|volume=24|pages=289–303 [289]|doi=10.1088/1475-4878/24/5/302}}</ref> adding circles indicating [[azimuth]]s on the [[horizon]].<ref>{{citation|title=The mathematics of Egypt, Mesopotamia, China, India, and Islam: a sourcebook|author=Victor J. Katz & Annette Imhausen|publisher=[[Princeton University Press]]|year=2007|isbn=0691114854|page=519}}</ref> The Arabs then took it during the [[Abbasid]] [[Caliphate]] and perfected it to be used to find the beginning of [[Ramadan]], the hours of [[prayer]] ([[Salah]]), the direction of [[Mecca]] ([[Qibla]]), and over a thousand other uses.<ref name=Winterburn/>
 
 
In the 10th century, [[Al-Sufi]] first described over 1,000 different uses of an astrolabe, in areas as diverse as astronomy, [[Islamic astrology|astrology, horoscopes]], [[Mariner's astrolabe|navigation]], [[surveying]], [[time]]keeping, [[Qibla]], [[Salah]], etc.<ref name=Winterburn>{{cite web|author=Dr. Emily Winterburn ([[National Maritime Museum]])|url=http://www.muslimheritage.com/topics/default.cfm?ArticleID=529|title=Using an Astrolabe|publisher=Foundation for Science Technology and Civilisation|year=2005|accessdate=2008-01-22}}</ref>
 
 
====Large astrolabe====
 
[[Ibn Yunus]] in the 10th century accurately observed more than 10,000 entries for the sun's position for many years using a large astrolabe with a diameter of nearly 1.4 meters.<ref name=Zaimeche/>
 
 
====Mechanical geared astrolabe====
 
The first [[Mechanical engineering|mechanical]] astrolabes with [[gear]]s were invented in the Muslim world, and were perfected by Ibn Samh (c. 1020). One such device with eight [[gear]]-wheels was also constructed by [[Abū Rayhān al-Bīrūnī]] in 996. These can be considered as an ancestor of the [[mechanical clock]]s developed by later Muslim engineers.<ref>{{cite web|url=http://www.usc.edu/dept/MSA/introduction/woi_knowledge.html|title=Islam, Knowledge, and Science|publisher=[[University of Southern California]]|accessdate=2008-01-22}}</ref>
 
 
[[Image:Astrolabe-Persian-18C.jpg|thumb|left|An 18th century Persian [[astrolabe]], kept at The [[Whipple Museum of the History of Science]] in [[Cambridge]], England.]]
 
 
====Navigational astrolabe====
 
The first [[Mariner's astrolabe|navigational astrolabe]] was invented in the Islamic world during the [[Middle Ages]], and employed the use of a [[Polar coordinate system|polar]] [[Map projection|projection]] system.<ref>Robert Hannah (1997). "''The Mapping of the Heavens'' by Peter Whitfield", ''Imago Mundi'' '''49''', pp. 161-162.</ref>
 
 
====Orthographical astrolabe====
 
[[Abū Rayhān al-Bīrūnī|Abu Rayhan al-Biruni]] invented and wrote the earliest treatise on the [[Orthographic projection (cartography)|orthographical]] astrolabe in the 1000s.<ref name=Khwarizm/>
 
 
[[Image:Astrolabio andalusí Toledo 1067 (M.A.N.) 01.jpg|thumb|An [[astrolabe]] from [[Al-Andalus]] dating back to 1067.]]
 
 
====Universal astrolabe (Saphaea)====
 
The first astrolabe instruments were used to read the rise of the time of rise of the [[Sun]] and fixed stars. The first universal astrolabes were later constructed in the Islamic world and which, unlike their predecessors, did not depend on the [[latitude]] of the observer and could be used anywhere on the Earth. The basic idea for a latitude-independent astrolabe was conceived in the 9th century by [[Habash al-Hasib al-Marwazi]] in Baghdad and the topic was later discussed in the early 11th century by [[Al-Sijzi]] in Persia.<ref>{{citation|title=The history of cartography|volume=2|authors=John Brian Harley, David Woodward|publisher=[[Oxford University Press]]|year=1992|isbn=0226316351|page=29}}</ref>
 
 
The first known universal astrolabe to be constructed was by Ali ibn Khalaf al-Shakkaz, an [[Medicine in medieval Islam|Arabic herbalist]] or [[apothecary]] in 11th century [[Al-Andalus]]. His instrument could solve problems of spherical astronomy for any geographic latitude, though in a somewhat more complicated fashion than the standard astrolabe. Another, more advanced and more famous, universal astrolabe was constructed by [[Abū Ishāq Ibrāhīm al-Zarqālī]] (Arzachel) soon after. His instrument became known in Europe as the "Saphaea".<ref>{{citation|title=The history of cartography|volume=2|authors=John Brian Harley, David Woodward|publisher=[[Oxford University Press]]|year=1992|isbn=0226316351|pages=28–9}}</ref> It was a universal lamina (plate) which "constituted a universal device representing a stereographic projection for the terrestrial equator and could be used to solve all the problems of spherical astronomy for any latitude."<ref name=King-1983-533/>
 
 
====Zuraqi====
 
The Zuraqi is a unique astrolabe invented by [[Al-Sijzi]] for a [[heliocentric]] planetary model in which the [[Earth's rotation|Earth is moving]] rather than the sky.<ref name=Nasr/>
 
 
====Planisphere====
 
[[Image:planisphere.jpg|thumb|right|The [[planisphere]] was invented by [[Abū Rayhān al-Bīrūnī]].]]
 
 
In the early 11th century, [[Abū Rayhān al-Bīrūnī]] invented and wrote the first treatise on the [[planisphere]], which was an early [[analog computer]].<ref name=Khwarizm/><ref>[[Will Durant]] (1950). ''[[The Story of Civilization]] IV: The Age of Faith'', p. 239-45.</ref> The astrolabe was a predecessor of the modern planisphere.
 
 
====Linear astrolabe====
 
A famous work by [[Sharaf al-Dīn al-Tūsī]] is one in which he describes the linear astrolabe, sometimes called the "staff of al-Tusi", which he invented.<ref>{{citation|url=http://www.britannica.com/eb/topic-342088/linear-astrolabe|contribution=Linear astrolabe|title=[[Encyclopædia Britannica]]|year=2007|accessdate=2008-01-22}}</ref>
 
 
====Astrolabic clock====
 
{{See also|Astronomical clock}}
 
 
[[Ibn al-Shatir]] invented the astrolabic [[clock]] in 14th century [[Syria]].<ref>{{Harv|King|1983|pp=545-546}}</ref>
 
 
===Analog computers===
 
Various [[analog computer]] devices were invented to compute the [[latitude]]s of the Sun, Moon, and planets, the [[ecliptic]] of the Sun, the time of day at which [[planetary conjunction]]s will occur, and for performing [[linear interpolation]].
 
 
====Equatorium====
 
The [[Equatorium]] was an [[analog computer]] invented by [[Abū Ishāq Ibrāhīm al-Zarqālī]] (Arzachel) in [[al-Andalus]], probably around 1015 CE. It is a mechanical device for finding the [[longitude]]s and positions of the [[Moon]], [[Sun]], and [[planet]]s, without calculation using a geometrical model to represent the [[celestial body]]'s mean and anomalistic position.<ref>{{Harv|Hassan}}</ref>
 
 
====Mechanical geared calendar computer====
 
[[Abu Rayhan Biruni]] also invented the first [[Mechanical engineering|mechanical]] [[lunisolar calendar]] [[Analog computer|computer]] which employed a [[gear train]] and eight [[gear]]-wheels.<ref>{{Harv|Hill|1985}}</ref> This was an early example of a fixed-[[wire]]d knowledge processing [[machine]].<ref name=Oren>Tuncer Oren (2001). "Advances in Computer and Information Sciences: From Abacus to Holonic Agents", ''Turk J Elec Engin'' '''9''' (1): 63-70 [64].</ref>
 
 
====Volvelle====
 
The [[volvelle]], also called a wheel chart, is a type of [[slide chart]], paper constructions with rotating parts. It is considered an early example of a paper [[analog computer]].<ref>{{cite journal|author=Nick Kanas|title=VOLVELLES! Early Paper Astronomical Computers|[[Mercury (magazine)|Mercury]]|issue=March-April 2005|url=http://www.astrosociety.org/pubs/mercury/34_02/computers.html|accessdate=2009-10-13}}</ref> The volvelle can be traced back to "certain [[Medicine in medieval Islam|Arabic treateses on humoral medicine]]"<ref>{{citation|title=On the Origin of Polyalphabetic Substitution|author=[[David Kahn (writer)|David Kahn]]|journal=[[Isis (journal)|Isis]]|volume=71|issue=1|date=March 1980|publisher=[[University of Chicago Press]]|url=http://www.jstor.org/stable/230316|accessdate=2009-10-13|pages=122–127 [126]}}</ref> and to Biruni (c. 1000) who made important contributions to the development of the volvelle.<ref>{{citation|title=State, Science and Economy in Traditional Societies: Some Problems in Weberian Sociology of Science|author=Bryan S. Turner|journal=British Journal of Sociology|volume=38|issue=1|date=March 1987|publisher=[[Wiley-Blackwell (publisher)|Blackwell Publishing]]|url=http://www.jstor.org/stable/590576|accessdate=2009-10-13|pages=1–23 [12]}}</ref> In the 20th century, the volvelle had many diverse uses.
 
 
[[Image:Torquetum.jpg|thumb|The [[torquetum]] was invented by [[Jabir ibn Aflah]] (Geber).]]
 
 
====Torquetum====
 
[[Jabir ibn Aflah]] (Geber) (c. 1100-1150) invented the [[torquetum]], an observational instrument and mechanical analog computer device used to transform between [[spherical coordinate system]]s.<ref>{{citation|first=R. P.|last=Lorch|title=The Astronomical Instruments of Jabir ibn Aflah and the Torquetum|journal=[[Centaurus (journal)|Centaurus]]|volume=20|issue=1|year=1976|pages=11–34|doi=10.1111/j.1600-0498.1976.tb00214.x}}</ref> It was designed to take and convert measurements made in three sets of coordinates: [[horizon]], [[equator]]ial, and [[ecliptic]].
 
 
====Castle clock with programmable analog computer====
 
{{Main|Castle clock}}
 
{{See also|Astronomical clock}}
 
 
In 1206, [[Al-Jazari]] invented his largest [[astronomical clock]], the "[[castle clock]]", which is considered to be the first [[Computer programming|programmable]] [[analog computer]].<ref name="Ancient Discoveries">{{citation|title=[[Ancient Discoveries]], Episode 11: Ancient Robots|publisher=[[History Channel]]|url=http://www.youtube.com/watch?v=rxjbaQl0ad8|accessdate=2008-09-06}}</ref> It displayed the [[zodiac]] and the [[Heliocentric orbit|solar]] and [[lunar orbit]]s. Another innovative feature of the clock was a [[wiktionary:pointer|pointer]] which traveled across the top of a [[gate]]way and caused automatic [[door]]s to open every [[hour]].<ref>{{Harv|Hill|1991}}</ref>
 
 
====Mechanical astrolabe with geared calendar computer====
 
In 1235, Abi Bakr of [[Isfahan]] invented a brass [[astrolabe]] with a [[gear]]ed [[calendar]] movement based on the design of [[Abū Rayhān al-Bīrūnī]]'s mechanical calendar computer.<ref>Silvio A. Bedini, Francis R. Maddison (1966). "Mechanical Universe: The Astrarium of Giovanni de' Dondi", ''Transactions of the American Philosophical Society'' '''56''' (5): 1-69.</ref> Abi Bakr's geared astrolabe uses a set of [[gear]]-wheels and is the oldest surviving complete mechanical geared [[machine]] in existence.<ref>{{cite web|url=http://www.mhs.ox.ac.uk/astrolabe/exhibition/gearing.htm|title=Astrolabe gearing|publisher=[[Museum of the History of Science, Oxford]]|year=2005|accessdate=2008-01-22}}</ref><ref>{{cite web|url=http://www.mhs.ox.ac.uk/students/03to04/Astrolabes/Starholder_history.html|title=History of the Astrolabe|publisher=[[Museum of the History of Science, Oxford]]}}</ref>
 
 
====Plate of Conjunctions====
 
In the 15th century, [[al-Kashi]] invented the Plate of Conjunctions, a computing instrument used to determine the time of day at which [[planetary conjunction]]s will occur,<ref>{{Harv|Kennedy|1947|p=56}}</ref> and for performing [[linear interpolation]].<ref name=Kennedy/>
 
 
====Planetary computer====
 
In the 15th century, [[al-Kashi]] also invented a mechanical planetary computer which he called the Plate of Zones, which could graphically solve a number of planetary problems, including the prediction of the true positions in [[longitude]] of the [[Sun]] and [[Moon]],<ref name=Kennedy>{{Harv|Kennedy|1950}}</ref> and the [[planet]]s in terms of [[elliptical orbit]]s;<ref>{{Harv|Kennedy|1952}}</ref> the [[latitude]]s of the Sun, Moon, and planets; and the [[ecliptic]] of the Sun. The instrument also incorporated an [[alhidade]] and [[ruler]].<ref>{{Harv|Kennedy|1951}}</ref>
 
 
===Astronomical clocks===
 
{{See also|Astronomical clock|Clock}}
 
 
The Muslims constructed a variety of highly accurate [[astronomical clock]]s for use in their observatories.<ref>{{Harv|Ajram|1992}}</ref>
 
 
====Water-powered astronomical clocks====
 
{{See also|Water clock}}
 
 
[[Al-Jazari]] invented monumental [[Water clock|water-powered]] [[astronomical clock]]s which displayed moving models of the [[Sun]], [[Moon]], and [[star]]s. His largest astronomical [[clock]] was the [[castle clock]], which is considered to be the first [[Computer programming|programmable]] [[analog computer]] (see [[#Analog computers|Castle clock with programmable analog computer]] above).<ref name="Ancient Discoveries"/>
 
 
====Spring-powered astronomical clock====
 
 
[[Taqi al-Din Muhammad ibn Ma'ruf|Taqi al-Din]] invented the first [[astronomical clock]] to be powered by [[Spring (device)|springs]], first described in his ''The Brightest Stars for the Construction of Mechanical Clocks'' (1556–1559).<ref name=Hassani>{{cite web|author=[[Salim Al-Hassani]]|title=The Astronomical Clock of Taqi Al-Din: Virtual Reconstruction|publisher=FSTC|url=http://muslimheritage.com/topics/default.cfm?ArticleID=947|date=19 June 2008|accessdate=2008-07-02}}</ref>
 
 
====Mechanical alarm clock====
 
{{See also|Alarm clock}}
 
 
[[Taqi al-Din Muhammad ibn Ma'ruf|Taqi al-Din]] invented the first mechanical [[alarm clock]], which he described in ''The Brightest Stars for the Construction of Mechanical Clocks'' (''Al-Kawākib al-durriyya fī wadh' al-bankāmat al-dawriyya'') in 1559. His alarm clock was capable of sounding at a specified time, which was achieved by means of placing a peg on the [[Dial (measurement)|dial]] wheel to when one wants the alarm heard and by producing an automated ringing device at the specified time.<ref name=Hassani/>
 
 
====Mechanical observational clock====
 
 
[[Taqi al-Din Muhammad ibn Ma'ruf|Taqi al-Din]] invented the "observational clock", which he described as "a mechanical [[clock]] with three [[Dial (measurement)|dials]] which show the [[hour]]s, the [[minute]]s, and the [[second]]s." This was the first clock to measure time in seconds, and he used it for astronomical purposes, specifically for measuring the [[right ascension]] of the [[star]]s. This is considered one of the most important innovations in 16th-century practical astronomy, as previous clocks were not accurate enough to be used for astronomical purposes.<ref name=Tekeli/> He further improved the observational clock, as described in his ''Sidrat al-muntaha'', using only one dial to represent the hours, minutes and seconds. He describes this observational clock as "a mechanical clock with a dial showing the hours, minutes and seconds and we divided every minute into five seconds."<ref name=Sayili>{{citation|first=Aydin|last=Sayili|authorlink=Aydin Sayili|title=The Observatory in Islam|year=1991|pages=289–305}} ([[cf.]] {{cite web|author=Dr. Salim Ayduz|title=Taqi al-Din Ibn Ma’ruf: A Bio-Bibliographical Essay|url=http://muslimheritage.com/topics/default.cfm?ArticleID=949|date=26 June 2008|accessdate=2008-07-04}})</ref>
 
 
===Dials===
 
Muslim astronomers and engineers invented a variety of [[Sundial|dials]] for [[timekeeping]], and for determining the times of the [[Salat|five daily prayers]].
 
 
====Sundials====
 
{{See also|Sundial}}
 
[[Image:SevillaGlorietaDelReloj01.JPG|thumb|left|A [[sundial]] in [[Seville]], [[Andalusia]], Spain.]]
 
 
Muslims made several important improvements to the theory and construction of [[sundial]]s, which they inherited from their [[Indian astronomy|Indian]] and [[Hellenistic civilization|Hellenistic]] predecessors. [[Al-Khwarizmi]] made tables for these instruments which considerably shortened the time needed to make specific calculations. Muslim sundials could also be observed from anywhere on the Earth. Sundials were frequently placed on mosques to determine the [[Salat times|time of prayer]]. One of the most striking examples was built in the 14th century by the ''muwaqqit'' (timekeeper) of the [[Umayyad Mosque]] in [[Damascus]], [[Ibn al-Shatir]].<ref>{{Harv|King|1999a|pp=168-9}}</ref> Muslim astronomers and engineers were the first to write instructions on the construction of horizontal sundials, vertical sundials, and polar sundials.<ref name=King-Astronomy>{{citation|first=David A.|last=King|contribution=Astronomy and Islamic society|pages=163–8}}, in {{Harv|Rashed|Morelon|1996|pp=128-184}}</ref>
 
 
Since ancient dials were nodus-based with straight hour-lines, they indicated unequal hours — also called temporary hours — that varied with the seasons, since every day was divided into twelve equal segments; thus, hours were shorter in winter and longer in summer. The idea of using hours of equal time length throughout the year was the innovation of Abu'l-Hasan [[Ibn al-Shatir]] in 1371, based on earlier developments in [[trigonometry]] by [[Muhammad ibn Jābir al-Harrānī al-Battānī]] (Albategni). Ibn al-Shatir was aware that "using a [[gnomon]] that is parallel to the Earth's axis will produce sundials whose hour lines indicate equal hours on any day of the year." His sundial is the oldest polar-axis sundial still in existence. The concept later appeared in Western sundials from at least 1446.<ref>{{cite web|title=History of the sundial|url=http://www.nmm.ac.uk/server/show/conWebDoc.353|publisher=[[National Maritime Museum]]|accessdate=2008-07-02}}</ref><ref>{{citation|title=The Sundial And Geometry|first=Lawrence|last=Jones|journal=North American Sundial Society|volume=12|issue=4|date=December 2005}}</ref>
 
 
====Navicula de Venetiis====
 
This was a universal horary [[Sundial|dial]] invented in 9th century [[Baghdad]]. It was used for accurate timekeeping by the Sun and Stars, and could be observed from any [[latitude]].<ref>{{Harv|King|2005}}</ref> This was later known in Europe as the "Navicula de Venetiis",<ref>{{Harv|King|2003}}</ref> which was considered the most sophisticated timekeeping instrument of the [[Renaissance]].<ref name=King/>
 
 
====Compass dial====
 
In the 13th century, [[Ibn al-Shatir]] invented the [[compass dial]], a [[time]]keeping device incorporating both a universal [[sundial]] and a magnetic [[compass]]. He invented it for the purpose of finding the times of [[Salah]] prayers.<ref>{{Harv|King|1983|pp=547-548}}</ref>
 
 
===Globes===
 
{{See also|Geography and cartography in medieval Islam}}
 
 
====Armillary sphere====
 
[[Image:Armillary sphere.png|thumb|right|An [[armillary sphere]].]]
 
 
An [[armillary sphere]] had similar applications to a [[celestial globe]]. No early Islamic armillary spheres survive, but several treatises on “the instrument with the rings” were written.
 
 
====Spherical astrolabe====
 
[[Image:Spherical astrolabe.jpg|thumb|left|The [[spherical astrolabe]] was invented by Islamic astronomers.]]
 
 
The [[spherical astrolabe]] was first produced in the [[Islamic Golden Age|Islamic world]].<ref>Emilie Savage-Smith (1993). "Book Reviews", ''Journal of Islamic Studies'' '''4''' (2): 296-299.
 
{{quote|"There is no evidence for the Hellenistic origin of the spherical astrolabe, but rather evidence so far available suggests that it may have been an early but distinctly Islamic development with no Greek antecedents."}}</ref> It was an Islamic variation of the astrolabe and the armillary sphere, of which only one complete instrument, from the 14th century, has survived.
 
 
====Terrestrial globe====
 
{{See also|Globe}}
 
 
The first terrestrial [[globe]] of the [[Old World]] was constructed in the [[Muslim world]] during the [[Middle Ages]],<ref>Mark Silverberg. [http://www.jfednepa.org/mark%20silverberg/origins.html Origins of Islamic Intolerence].</ref> by [[Islamic geography|Muslim geographers]] and astronomers working under the [[Abbasid]] [[caliph]], [[Al-Ma'mun]], in the 9th century.<ref>{{citation|first=Richard|last=Covington|journal=[[Saudi Aramco World]], May-June 2007|year=2007|pages=17–21|url=http://www.saudiaramcoworld.com/issue/200703/the.third.dimension.htm|accessdate=2008-07-06}}</ref> Another example was the terrestrial globe introduced to [[Beijing]] by the Persian astronomer [[Jamal ad-Din (astronomer)|Jamal ad-Din]] in 1267.<ref>{{citation|title=The Image of the Spherical Earth|author=David Woodward|journal=[[Perspecta (journal)|Perspecta]]|volume=25|year=1989|pages=3–15 [9]|publisher=[[MIT Press]]|url=http://www.jstor.org/stable/1567135|accessdate=2010-02-22}}</ref>
 
 
====Celestial globes====
 
[[Celestial globe]]s were used primarily for solving problems in celestial astronomy. Today, 126 such instruments remain worldwide, the oldest from the 11th century. The altitude of the sun, or the [[Right Ascension]] and [[Declination]] of stars could be calculated with these by inputting the location of the observer on the [[meridian (geography)|meridian]] ring of the [[globe]].
 
 
In the 12th century, [[Jabir ibn Aflah]] (Geber) was "the first to design a portable celestial sphere to measure and explain the movements of celestial objects."<ref>{{cite web|title=An overview of Muslim Astronomers|url=http://www.muslimheritage.com/topics/default.cfm?ArticleID=232|publisher=FSTC Limited|date=26 December 2001|accessdate=2008-02-01}}</ref>
 
 
====Seamless celestial globe====
 
The [[Seam (metallurgy)|seamless]] [[celestial globe]] invented by Muslim metallurgists and instrument-makers in [[Mughal India]], specifically [[Lahore]] and [[Kashmir]], is considered to be one of the most remarkable feats in [[metallurgy]] and [[engineering]]. All [[globe]]s before and after this were seamed, and in the 20th century, it was believed by metallurgists to be technically impossible to create a metal globe without any [[Seam (metallurgy)|seams]]. It was in the 1980s, however, that Emilie Savage-Smith discovered several celestial globes without any seams in Lahore and Kashmir. The earliest was invented in Kashmir by the Muslim metallurgist Ali Kashmiri ibn Luqman in 998 AH (1589-90 CE) during [[Akbar the Great]]'s reign; another was produced in 1070 AH (1659-60 CE) by Muhammad Salih Tahtawi with Arabic and Sanskrit inscriptions; and the last was produced in Lahore by a Hindu metallurgist Lala Balhumal Lahuri in 1842 during [[Jagatjit Singh Bahadur]]'s reign. 21 such globes were produced, and these remain the only examples of seamless metal globes. These Mughal metallurgists developed the method of [[lost-wax casting]] in order to produce these globes.<ref>{{citation|first=Emilie|last=Savage-Smith|title=Islamicate Celestial Globes: Their History, Construction, and Use|publisher=Smithsonian Institution Press, Washington, D.C.|year=1985}}</ref><ref name=Kazi/>
 
 
These seamless celestial globes are considered to be an unsurpassed feat in metallurgy, hence some consider this achievement to be comparable to that of the [[Great Pyramid of Giza]] which was considered an unsurpassed feat in [[architecture]] until the 19th century.<ref name=Kazi>{{cite web|first=Najma|last=Kazi|title=Seeking Seamless Scientific Wonders: Review of Emilie Savage-Smith's Work|url=http://www.muslimheritage.com/topics/default.cfm?articleID=832|publisher=FSTC Limited|date=24 November 2007|accessdate=2008-02-01}}</ref>
 
 
===Optical instruments===
 
{{See also|Islamic physics}}
 
 
====Observation tube====
 
The first reference to an "observation tube" is found in the work of [[al-Battani]] (Albatenius) (853-929), and the first exact description of the observation tube was given by [[al-Biruni]] (973-1048), in a section of his work that is "dedicated to verifying the presence of the new crescent on the horizon." Though these early observation tubes did not have [[Lens (optics)|lenses]], they "enabled an observer to focus on a part of the sky by eliminating [[light]] interference." These observation tubes were later adopted in [[Latin]]-speaking Europe, where they influenced the development of the [[telescope]].<ref>Regis Morelon, "General Survey of Arabic Astronomy", pp. 9-10, in {{Harv|Rashed|Morelon|1996|pp=1-19}}</ref>
 
 
====Experimental device with apertures====
 
In order to prove that "[[light]] is emitted from every point of the [[moon]]'s illuminated surface," [[Ibn al-Haytham]] (Alhazen) built an "ingenious [[experiment]]al device" showing "that the [[radiance|intensity]] of the light-spot formed by the projection of the [[moonlight]] through two small [[aperture]]s onto a screen diminishes constantly as one of the apertures is gradually blocked up."<ref name=Toomer/>
 
 
====Magnifying lens====
 
The first [[Optics|optical]] research to describe a [[magnifying lens]] used in an instrument was found in a book called the ''[[Book of Optics]]'' (1021) written by [[Alhazen|Ibn al-Haytham]] (Alhazen).<ref name= Sabra2>Sabra, A. I. & Hogendijk, J. P. (2003), The Enterprise of Science in Islam: New Perspectives, MIT Press, pp. 85-118, ISBN 0262194821</ref> His descriptions were fundamental to the development of the telescope and helped set the parameters in [[Europe]] for the later advances in telescopic technology.<ref>O. S. Marshall (1950). "Alhazen and the Telescope", Astronomical Society of the Pacific Leaflets 6, p. 4</ref> His additional work in light [[refraction]], [[parabolic mirror]]s, as well as the creation of other instruments such as the [[camera obscura]], also helped spark the [[Scientific Revolution]].<ref name="Sabra2"/><ref>[[Richard Powers]] (University of Illinois), Best Idea; Eyes Wide OpenNew York Times, April 18, 1999.</ref>
 
 
====Telescope====
 
[[Taqi al-Din Muhammad ibn Ma'ruf|Taqi al-Din]] describes a long-distance [[Magnification|magnifying]] device in his ''Book of the Light of the Pupil of Vision and the Light of the Truth of the Sights'' around 1574, which may have possibly been an early rudimentary [[telescope]]. He describes his device as an instrument that makes objects located far away appear closer to the observer, and that the instrument helps to see distant objects in detail by bringing them very close. Taqi al-Din states that he wrote another treatise (which has not survived to the present day) explaining the way this instrument is made and used. There is some confusion as to what he was describing since he also said his invention was similar to one used by ancient Greeks at the Tower of [[Alexandria]].<ref name="Topdemir"/>
 
 
The earliest mention of telescopic observations in Islamic astronomy occurs in the ''[[Zij|Zij-i Muhammad Shahi]]''. It was compiled in early 18th-century India for the Hindu king [[Jai Singh II of Amber]], who states in the text: "telescopes were constructed in my kingdom and using them a number of observations were carried out."<ref name=Ansari/>
 
 
===Quadrants===
 
A number of [[mural instrument]]s, including several different [[Quadrant (instrument)|quadrants]] and [[Sextant (astronomical)|sextants]], were invented by Muslim astronomers and engineers.
 
 
[[Image:Tycho instrument augsburg quadrant 20.jpg|thumb|The [[Quadrant (instrument)|quadrant]] was invented by [[Muhammad ibn Mūsā al-Khwārizmī]]. This illustration was drawn by [[Tycho Brahe]].]]
 
 
====Sine quadrant====
 
{{See also|Sine quadrant}}
 
 
The [[sine quadrant]], invented by [[Muhammad ibn Mūsā al-Khwārizmī]] in 9th century [[Baghdad]], was used for astronomical calculations.<ref name=King-2002/> Also known as the "Sinecal Quadrant" (the Arabic term for it is "Rubul Mujayyab"), it was used for solving trigonometric problems and taking astronomical observations. It was developed by al-Khwarizmi in the 9th century and remained prevalent until the 19th century. Its defining feature is a [[graph paper]] like grid on one side that is divided into sixty equal intervals on each axis and is also bounded by a 90 degree graduated arc. A cord was attached to the apex of the quadrant with a bead at the end of it to act as a plumb bob. They were also sometimes drawn on the back of astrolabes.<ref name=King-1987>{{citation|last=King|first=David A.|year=1987|title=Islamic Astronomical Instruments|publisher=Variorum|publication-place=London}}</ref>
 
 
====Horary quadrant====
 
The first horary quadrant for specific [[latitude]]s, was invented by [[Muhammad ibn Mūsā al-Khwārizmī]] in 9th century Baghdad, center of the development of quadrants.<ref name=King-2002/> It was used to determine time (especially the times of prayer) by observations of the Sun or stars.<ref>{{Harv|King|1999a|pp=167-8}}</ref> The horary quadrant could be used to find the time either in equal or unequal (length of the day divided by twelve) hours. Different sets of markings were created for either equal or unequal hours. For measuring the time in equal hours, the horary quadrant could only be used for one specific latitude while a quadrant for unequal hours could be used anywhere based on an approximate formula. One edge of the quadrant had to be aligned with the sun, and once aligned, a bead on the end of a plumbline attached to the centre of the quadrant showed the time of the day.<ref name=King-1987/>
 
 
====Universal horary quadrant (Quadrans Novus)====
 
The universal horary quadrant was an ingenious mathematical device invented by [[al-Khwarizmi]] in 9th century [[Baghdad]] and which was later known as the "Quadrans Vetus" (Old Quadrant) in medieval Europe from the 13th century. It could be used for any [[latitude]] on Earth and at any time of the year to determine the time in hours from the [[altitude]] of the Sun. This was the second most widely used astronomical instrument during the [[Middle Ages]] after the astrolabe. One of its main purposes in the Islamic world was to determine the times of [[Salah]].<ref name=King-2002>{{Harv|King|2002|pp=237-238}}</ref>
 
 
[[Image:Ulugh Beg observatory.JPG|thumb|left|[[Ulugh Beg]]'s [[mural instrument|mural]] [[Sextant (astronomical)|sextant]], constructed in [[Samarkand]], [[Uzbekistan]], during the 15th century.]]
 
 
====Astrolabic/Almucantar quadrant (Quadrans Vetus)====
 
The astrolabic or [[almucantar]] quadrant was invented in the medieval Islamic world, and it employed the use of [[trigonometry]]. The term "almucantar" is itself derived from Arabic.<ref>Elly Dekker (1995), "An unrecorded medieval astrolabe quadrant from c. 1300", ''Annals of Science'' '''52''' (1): 1-47 [6].</ref> The almucantar quadrant was originally modified from the [[astrolabe]].<ref name=King-Astronomy/> It was invented in [[Egypt]] in the 11th or 12th century, and was later known in Europe as the "Quadrans Vetus" (New Quadrant).<ref>{{Harv|King|Cleempoel|Moreno|2002|p=333}}</ref> It was intended as a simplified alternative to the astrolabe serving a specific latitude. According to David King:<ref name=King-1983-533>{{Harv|King|1983|p=533}}</ref>
 
 
{{quote|"This was an invention of some consequence, for the astrolabe, fitted with a series of plates for different latitudes, was neither a practical device nor an accurate observational instrument. Also, being made of brass, it was expensive. The almucantar quadrant, on the other hand, could be made of wood and was an extremely practical device with which one could solve all the problems solvable with an astrolabe, for a particular latitude. The back of such a quandrant could carry a trigonometric grid called a sine quadrant for solving all manner of computational problems."}}
 
 
====Universal quadrant (Shakkāzīya)====
 
The universal (shakkāzīya) quadrant was used for solving astronomical problems for any latitude. These quadrants had either one or two sets of shakkāzīya grids and were developed in the 14th century in [[Syria]]. Some astrolabes are also printed on the back with the universal quadrant like an astrolabe created by Ibn al-Sarrāj.<ref name=King-1987/> The Shakkaziya quadrant produced by Jamal al-Din al-Maridini was an [[analog computer]] for solving problems of spherical astronomy.<ref>{{citation|last=King|first=David A.|year=1974|title=An analog computer for solving problems of spherical astronomy: The Shakkaziya quadrant of Jamal al-Din al-Maridini|journal=Archives Internationales d'Histoire des Sciences (International Archives on the History of Science)|volume=24|pages=219–42}}</ref> By the time of the [[Mamluk Sultanate (Cairo)|Mamluk Sultanate]], Muslim astronomers "developed the quadrant to all conceivable limits; it virtually replaced the astrolabe in Syria and Egypt in Mamluk and [[Ottoman Empire|Ottoman]] times."<ref name=King-1983-533/>
 
 
===Sextants===
 
====Mural sextant====
 
The first [[Sextant (astronomical)|sextant]] was constructed in [[Ray, Iran|Ray]], Iran, by [[Abu-Mahmud al-Khujandi]] in 994. It was a very large [[Mural instrument|mural]] sextant that achieved a high level of accuracy for [[astronomy|astronomical]] measurements, which he described his in his treatise, ''On the obliquity of the ecliptic and the latitudes of the cities''.<ref>{{MacTutor|id=Al-Khujandi|title=Al-Khujandi}}</ref>
 
 
====Fakhri sextant====
 
In the 15th century, [[Ulugh Beg]] constructed the Fakhri sextant, which had a radius of approximately 36 meters. Constructed in [[Samarkand]], [[Uzbekistan]], the arc was finely constructed with a staircase on either side to provide access for the assistants who performed the measurements.
 
 
====Framed sextant====
 
At the [[Istanbul observatory of Taqi al-Din]] between 1577 and 1580, [[Taqi al-Din Muhammad ibn Ma'ruf|Taqi al-Din]] invented the ''mushabbaha bi'l manattiq'', a framed sextant with cords for the determination of the [[equinox]]es similar to what [[Tycho Brahe]] later used.<ref name=Tekeli>{{cite encyclopedia | first = Sevim | last = Tekeli | title = Taqi al-Din | year = 1997 | encyclopedia = Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures | publisher = [[Kluwer Academic Publishers]] | isbn = 0792340663 | url = http://www.springer.com/philosophy/philosophy+of+sciences/book/978-1-4020-4425-0 }}</ref>
 
 
===Other instruments===
 
Various other astronomical instruments were also invented in the Islamic world:
 
 
*'''Astronomical [[compass]]''': The first astronomical uses of the magnetic compass is found in a treatise on astronomical instruments written by the [[Yemen]]i [[sultan]] al-[[Ashraf]] (died 1296) in 1282. This was the first reference to the compass in astronomical literature.<ref>Emilie Savage-Smith (1988), "Gleanings from an Arabist's Workshop: Current Trends in the Study of Medieval Islamic Science and Medicine", ''[[Isis (journal)|Isis]]'' '''79''' (2): 246-266 [263].</ref>
 
*'''Dry [[compass]]''': In 1282, al-Ashraf also developed an improved compass for use as a "[[Qibla]] indicator" instrument in order to find the direction to [[Mecca]]. Al-Ashraf's instrument was one of the earliest dry compasses, and appears to have been invented independently of [[Peter Peregrinus]].<ref>{{citation|title=Two Early Arabic Sources On The Magnetic Compass|first=Petra G.|last=Schmidl|journal=Journal of Arabic and Islamic Studies|year=1996-1997|volume=1|pages=81–132}}</ref>
 
[[Image:Alidade for ceiling projector.JPG|right|thumb|An [[alidade]].]]
 
*'''[[Alhidade]]''': The alhidade was invented in the Islamic world, while the term "alhidade" is itself derived from Arabic.
 
*'''[[Compendium]] instrument''': A compendium was a multi-purpose astronomical instrument, first constructed by the Muslim astronomer [[Ibn al-Shatir]] in the 13th century. His compendium featured an [[alhidade]] and polar [[sundial]] among other things. Al-Wafa'i developed another compendium in the 15th century which he called the "equatorial circle", which also featured a horizontal sundial. These compendia later became popular in [[Renaissance]] Europe.<ref name=King-Astronomy/>
 
*'''[[Orthogonality|Orthogonal]] and [[regular grid]]s''': Islamic [[Quadrant (instrument)|quadrants]] used for various astronomical and timekeeping purposes from the 10th century introduced [[orthogonal]] and [[regular grid]]s and markings that are identical to modern [[graph paper]].<ref>Josef W. Meri (2006), ''Medieval Islamic Civilization: An Encyclopedia'', p. 75, [[Taylor and Francis]], ISBN 0415966914.</ref><ref>{{Harv|King|1999b|p=17}}</ref>
 
*'''[[Qibla]] indicators''': In 17th century [[Safavid dynasty|Safavid Persia]], two unique [[brass]] instruments with [[Mecca]]-centred [[world map]]s engraved on them were produced primarily for the purpose of finding the [[Qibla]]. These instruments were engraved with [[Cartography|cartographic]] [[Grid reference|grids]] to make it more convenient to find the direction and distance to Mecca at the centre from anywhere on the Earth, which may be based on cartographic grids dating back to 10th century [[Baghdad]].<ref name=King>{{Harv|King|2004}}</ref> One of the two instruments, produced by Muhammad Husayn,<ref>{{Harv|Iqbal|2003}}</ref> also had a [[sundial]] and [[compass]] attached to it.<ref>{{Harv|King|1997|p=62}}</ref>
 
*'''[[Shadow square]]''': The shadow square was an instrument used to determine the linear height of an object, in conjunction with the [[alidade]], for angular observations.<ref>{{cite web|url=http://www.nmm.ac.uk/collections/search/lightbox.cfm/category/90286|title=Shadow square|publisher=[[National Maritime Museum]]|accessdate=2008-01-22}}</ref> It was invented by [[Muhammad ibn Mūsā al-Khwārizmī]] in 9th century Baghdad.<ref>{{Harv|King|2002|pp=238-239}}</ref>
 
 
==List of notable treatises==
 
===Zij treatises===
 
{{Main|Zij}}
 
 
*[[Ibrahim al-Fazari]] (d. 777) and [[Muhammad al-Fazari]] (d. 796/806)
 
**''Az-Zij ‛alā Sinī al-‛Arab'' (c. 750)
 
*[[Yaqūb ibn Tāriq]] (d. 796)
 
**''Az-Zij al-Mahlul min as-Sindhind li-Darajat Daraja''
 
*[[Muhammad ibn Mūsā al-Khwārizmī]] ([[Latin]]ized as ''Algorismi'') (c. 780-850)
 
**''Zij al-Sindhind'' (c. 830)
 
*[[Muhammad ibn Jābir al-Harrānī al-Battānī]] (Latinized as ''Albategni'') (853-929)
 
**''Az-Zij as-Sabi''
 
*[[Abd Al-Rahman Al Sufi]] (Latinized as ''Azophi'') (903-986)
 
**''[[Book of Fixed Stars]]'' (c. 964)
 
*[[Ibn Yunus]] (c. 950–1009)
 
**''Zij al-Kabir al-Hakimi''
 
*[[Al-Zarqali]] (Latinized as ''Arzachel'') (1028–1087)
 
**''[[Tables of Toledo]]''
 
*[[Abu l-Fath al-Khazini]] (fl. 1115–1130)
 
**''Az-Zij as-Sanjarī'' (''Sinjaric Tables'') (1115–1116)
 
*[[Nasīr al-Dīn al-Tūsī]] (1201–1274)
 
**''[[Zij-i Ilkhani]]'' (''Ilkhanic Tables'') (1272)
 
*[[Jamshīd al-Kāshī]] (1380–1429)
 
**''Khaqani Zij''
 
*[[Ulugh Beg]] (1394–1449)
 
**''[[Zij-i-Sultani]]'' (1437)
 
*[[Taqi al-Din Muhammad ibn Ma'ruf|Taqi al-Din]] (1526–1585)
 
**''Unbored Pearl'' (1577–1580)
 
 
===Almanacs===
 
The word "[[Almanac]]" is an [[Arabic language|Arabic]] word.<ref>{{Harv|Glick|Livesey|Wallis|2005|p=29}}</ref> The modern almanac differs from earlier astronomical tables (such as the earlier [[Babylonian astronomy|Babylonian]], Ptolemaic and [[Zij]] tables) in the sense that "the entries found in the almanacs give directly the positions of the celestial bodies and need no further computation", in contrast to the more common "auxiliary astronomical tables" based on Ptolemy's ''Almagest''. The earliest known almanac in this modern sense is the ''Almanac of Azarqueil'' written in 1087 by [[Abū Ishāq Ibrāhīm al-Zarqālī]] (Latinized as Azarqueil) in [[Toledo, Spain|Toledo]], [[Al-Andalus]]. The work provided the true daily positions of the sun, moon and planets for four years from 1088 to 1092, as well as many other related tables. A [[Latin]] translation and adaptation of the work appeared as the ''[[Tables of Toledo]]'' in the 12th century and the ''[[Alfonsine tables]]'' in the 13th century.<ref>{{Harv|Glick|Livesey|Wallis|2005|p=30}}</ref>
 
 
===Treatises on instruments===
 
In the 12th century, [[al-Khazini]] wrote the ''Risala fi'l-alat'' (''Treatise on Instruments'') which had seven parts describing different [[scientific instrument]]s: the [[Triquetrum (astronomy)|triquetrum]], [[dioptra]], a [[triangle|triangular]] instrument he invented, the [[Quadrant (instrument)|quadrant]] and [[Sextant (astronomical)|sextant]], the [[astrolabe]], and original instruments involving [[Reflection (physics)|reflection]].<ref>Robert E. Hall (1973). "Al-Biruni", ''Dictionary of Scientific Biography'', Vol. VII, p. 338.</ref>
 
 
In 14th century [[Egypt]], Najm al-Din al-Misri (c. 1325) wrote a treatise describing over 100 different types of scientific and astronomical instruments, many of which he invented himself.<ref name=King/>
 
 
In 1416, [[al-Kashi]] wrote the ''Treatise on Astronomical Observational Instruments'', which described a variety of different instruments, including the [[Triquetrum (astronomy)|triquetrum]] and [[armillary sphere]], the [[Equinox|equinoctial]] armillary and [[Solstice|solsticial]] armillary of [[Mo'ayyeduddin Urdi]], the [[sine]] and [[versine]] instrument of Urdi, the [[Sextant (astronomical)|sextant]] of [[al-Khujandi]], the Fakhri sextant at the [[Samarqand]] observatory, a double quadrant [[Azimuth]]-[[altitude]] instrument he invented, and a small armillary sphere incorporating an [[alhidade]] which he invented.<ref>{{Harv|Kennedy|1961|pp=104-107}}</ref>
 
 
===Other works===
 
*[[Ja'far Muhammad ibn Mūsā ibn Shākir]] (Latinized as ''Mohammed Ben Musa'') (800-873)
 
**''Book on the motion of the orbs''
 
**''Astral Motion''
 
**''The Force of Attraction''
 
*[[Ahmad ibn Muhammad ibn Kathīr al-Farghānī]] (Latinized as ''Alfraganus'') (d. 850)
 
**''Elements of astronomy on the celestial motions'' (c. 833)
 
**''Kitab fi Jawami Ilm al-Nujum''
 
*[[Ibn al-Haytham]] (Latinized as ''Alhacen'') (965-1039)
 
**''On the Configuration of the World''
 
**''Doubts concerning Ptolemy'' (c. 1028)
 
**''The Resolution of Doubts'' (c. 1029)
 
**''The Model of the Motions of Each of the Seven Planets'' (1029–1039)
 
*[[Abū Rayhān al-Bīrūnī]] (973–1048)
 
**''Kitab al-Qanun al-Mas'udi'' (Latinized as ''Canon Mas’udicus'') (1031)
 
*[[Juzjani, Abu Ubaid|Abu Ubayd al-Juzjani]] (c. 1070)
 
**''Tarik al-Aflak'' (1070)
 
*''Al-Istidrak ala Batlamyus'' (''Recapitulation regarding Ptolemy'') (11th century)
 
*[[Al-Khazini]] (fl. 1115–1130)
 
**''Risala fi'l-alat'' (''Treatise on Instruments'')
 
*[[Nasīr al-Dīn al-Tūsī]] (1201–1274)
 
**''Al-Tadhkirah fi'ilm al-hay'ah'' (''Memento in astronomy'')
 
*[[Najm al-Dīn al-Qazwīnī al-Kātibī]] (d. 1277)
 
**''Hikmat al-'Ain''
 
*[[Qutb al-Din al-Shirazi]] (1236–1311)
 
**''The Limit of Accomplishment concerning Knowledge of the Heavens''
 
*[[Ibn al-Shatir]] (1304–1375)
 
**''A Final Inquiry Concerning the Rectification of Planetary Theory''
 
*[[Ali Kuşçu|Ali al-Qushji]] (d. 1474)
 
**''Concerning the Supposed Dependence of Astronomy upon Philosophy''
 
*[[Shams al-Din al-Khafri]] (d. 1525)
 
**''The complement to the explanation of the memento''
 
 
==Arabic star names==
 
{{Main|List of Arabic star names}}
 
 
One of the Islamic astronomy's accomplishments was in naming the [[stars]]. In ancient times, astronomers never named the stars, but identified them by descriptions. It was Islamic astronomy which began the tradition of giving specific names to individual stars.
 
 
Most of the modern names for numerous [[star]]s, and many of the [[constellation]]s, are derived from their [[Arabic language]] names. Examples include: [[Acamar]], [[Aldebaran]], [[Algol]], [[Altair]], [[Theta Pegasi|Baham]], [[Baten Kaitos]], [[Caph]], [[Dabih]], [[Edasich]], [[Furud]], [[Gienah]], [[Beta Centauri|Hadar]], [[Epsilon Boötis|Izar]], [[Jabbah]], [[Keid]], [[Lesath]], [[Epsilon Boötis|Mirak]], [[Nashira]], [[Okda]], [[Phad]], [[Rigel]], [[Gamma Cygni|Sadr]], [[Tarf]], and [[Vega]], as well as a number of other stars. Some of these names originated in the pre-Islamic [[Arabian Peninsula]], but many came later, some as translations of ancient descriptions and others of unknown origin.<ref>{{cite web|url=http://astro.isi.edu/reference/starnames.txt|title=Arabic Star names}}</ref>
 
 
===Description===
 
Very old star names originated among people who lived in the [[Arabian Peninsula]] more than a thousand years ago, before the rise of [[Islam]]. Many [[Arabic language]] star names sprang up later in history, as translations of ancient [[Greek language]] descriptions from [[Egypt]] (in turn, many of these are derived from [[Akkadian language]] terms in [[Babylonian astronomy]]).
 
 
The [[Egyptian astronomy|Egyptian astronomer]], [[Ptolemy|Claudius Ptolemy]], in his ''[[Almagest]]'' (2nd century), tabulated the celestial position and brightness (visual magnitude) of 1,025 stars. Ptolemy's book was translated into Arabic in the 8th and 9th centuries and became famous in Europe as a 12th-century Latin translation. Many of the Arabic-language star descriptions in the ''Almagest'' came to be widely used as names for stars.
 
 
Ptolemy did not name the stars, but used a strategy of "figure reference" to identify stars according to their position within a familiar constellation or asterism (e.g., "in the right shoulder of The Hunter"). [[Astronomy in medieval Islam |Muslim astronomers]] adopted some of these descriptions as proper names for stars, and added names from traditional Arabic star lore, which they recorded in various [[Zij]] treatises. The most notable of these is the ''[[Book of Fixed Stars]]'' written by the [[Muslim]] astronomer [[Abd al-Rahman al-Sufi]] (known as ''Azophi'' in the West), who thoroughly illustrated all the stars known to him along with their observations, descriptions, positions, magnitudes, brightness, and color.
 
 
In Europe, during the Middle Ages and Renaissance, many ancient star names were copied or translated incorrectly by various writers, some of whom did not know the Arabic language very well. As a result, the history of a star's name can be complicated.<ref>[http://web.archive.org/web/20070928043446/http://www.rmsc.org/planetarium/qandi/snames.htm "Star Names: Where Do They Come From? And Can You Buy One?"], RMSC Strasenburgh Planetarium Information Bulletin #19 December 1996, (archived 2007)</ref>
 
 
==See also==
 
*[[Arab and Persian astrology]]
 
*[[Egyptian astronomy]]
 
*[[Hebrew astronomy]]
 
*[[History of astronomy]]
 
*[[Iraqi astronomy]]
 
*[[Inventions in the Muslim world]]
 
**[[Inventions in the medieval Islamic world]]
 
**[[Inventions in the modern Islamic world]]
 
*[[Islamic astrology]]
 
*[[Islamic Golden Age]]
 
*[[Islamic science and technology]]
 
*[[List of Arabic star names]]
 
*[[List of Arab scientists and scholars]]
 
*[[List of Iranian scientists and scholars]]
 
*[[List of Muslim astronomers]]
 
*[[List of Muslim scientists]]
 
*[[Physics in medieval Islam]]
 
*[[Sufi cosmology]]
 
*[[Zij]]
 
 
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==External links==
 
*[http://www.auass.org The Arab Union for Astronomy and Space Sciences (AUASS)]
 
*[http://www.kacst.edu.sa/eng/inst/agri/dept4.php King Abdul Aziz Observatory]
 
*[http://www.hps.cam.ac.uk/starry/isaslabecalen.html History of Islamic Astrolabes]
 
 
{{Islamic astronomy}}
 
{{Islamic studies}}
 
 
{{DEFAULTSORT:Astronomy In Medieval Islam}}
 
[[Category:Islamic astronomy| ]]
 
[[Category:History of astronomy]]
 
[[Category:Islamic Golden Age]]
 

Revision as of 14:20, 10 December 2016

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