Islamic Civilization

Observatories

 The established wisdom holds that observatories are a late invention of Europe.[1] Those who recognise the Islamic origins of observatories, still consider them a late and a short-lived institution.[2] Here follows evidence proving both positions wrong.

Sedillot insists that the observatory as a distinct scientific institution for observation, and where astronomy and allied subjects were taught, owes its origin to Islam.[3] Sayili, in his ground breaking work, also demonstrates that the observatory as a scientific, specialised institution, is owed to Islam.[4] These views are correct as they fit within the pattern already observed in relation to many breakthroughs, i.e the close ties between science and observance of the faith, between the spiritual and the practical.[5] On the spiritual side, the zeal to contemplate and observe God’s creation, and the urge to understand its vastness, as found and stipulated in the Qur’an, and as expressed by nearly all Muslim astronomers, was a major reason for observation and study of the planets. The Qur’an in sura 50, verse 6 says:

"Do they not look at the sky above them, how We have built it and adorned it, and there are no rifts in it."

sura 31, verse 10 says:

"(God) created the heavens without any pillars that you can see..."

On the practical side, in observing their religious practices Muslims came across problems they had to resolve.[6] This entailed, for instance, accuracy in the observation of the planets so as to determine many religious matters, the emphasis on precise results being such that theologians saw it was necessary to be involved in observations.[7] This emphasis, in turn, led to a greater role for patronage of astronomy, the use of precise instruments, and also the need for organised teams of scholars, involved in diverse sciences (geometry, arithmetic, instrument designers, etc) working together, making observations in groups, and checking each others’ observations.[8] Hence, out of necessity, the observatory and observation became established within Islam.

The earliest date generally agreed upon for the erection of observatories is the 9^th century, when state run observatories were established simultaneously in Baghdad  and Damascus . Prior to this, astronomers used their homes for the purpose of observation. Al-Hassan of Baghdad (fl.825) (known for his book on the measurement of the sphere) was one of the earliest to build an astronomical observatory in his home.[9] He was one of the three Banu Musa brothers, who made observations from their house located on the Tigris River. They studied The Ursa Major (or the Great Bear), measured maximum and minimum altitudes of the sun, and made observations of lunar eclipses.[10] The Banu Musa also made observations at Samarra,[11] and they apparently arranged for simultaneous observations of a lunar eclipse in Samarra and Nishapur in order to determine their difference of longitude.[12] One of their Samarra observations was that of an autumnal equinox.[13] From a statement concerning their measurement of a meridian height of the sun, wherein the expression ‘observation in both circles’ occurs, Shoy guesses that they may have used an armillary sphere, or perhaps solsticial and equinoctial  armillas.[14]

Ibn Sina , Al-Battani , Al-Farghani also had their own home based observatories. Al-Battani's observatory was located in Raqqa, from where he made observations covering forty years (887 to 918), whilst Ibn Sina's observatory was in Hamadan. Ibn Sina and al-Biruni were preoccupied with increasing the precision of the instruments: Ibn Sina invented a device in principle equivalent to the micrometer,[15] whilst Al-Biruni  provided what was to be a forerunner of the method of transversals.[16]

The first observatory, in the truer sense, was at Shamsiyah (Baghdad ), set up by Caliph Al-Mamun around 828-829. It was associated with the scientific academy of Bayt al-Hikma  (House of Wisdom) (also set up by Al-Mamun.) Simultaneously  another observatory was set up on the outskirts of Damascus  on Mount Qasiyun.[17] Al-Biruni  mentions an observation of autumnal equinox made at Qasiyun, in connection with which a comparison seems to have been made with Baghdad on the basis of an eight degree value for the difference of longitude between the two cities.[18]  Shamsiyah was headed by Ibn Al-Naubakht and Al-Khwarizmi , whilst at Damascus, one of the superintendents was Abu Mansur (b. 885).[19] The ablest astronomers of the era were brought together at the expense of the sovereign, charged most particularly with proving the data in Ptolemy’s Almagest, and of making observations of the Sun and the Moon for one year.[20] Amongst such astronomers were Al-Jauhari and Yahia B. Abi Mansur. Al-Jauhari (fl. 830) participated in the astronomical observations made in Baghdad (829-30) and Damascus (832-3), and was in charge of the construction of astronomical instruments, as well as being the author of the Kitab al-Zij (Book of Astronomical Tables), based on the observations made in Baghdad.[21] Habash al-Hasib tells how Caliph al-Mamun ordered Khalid al-Marwrudhi, another astronomer involved, to make ready instruments of the greatest possible perfection, and to observe the heavenly bodies for a whole year, which Khalid did, ‘thus attaining to the truth concerning the position of the sun and the moon across the heavens, and when this was done, Al-Mamun ordered the preparation of a canon containing all this material for those desirous of learning that science.’[22] In both Baghdad and Damascus observations were made of the Sun, the Moon and planets, and results were presented in a new set of tables, or Zij, known as the Ma'muni or Mumtahan (tested) Zij.[23] Work was done on the solar year, the obliquity, the eccentricity of the orbit of the sun, and on the location of its apogee.[24] Observation  resulted in the discovery of the movement of the solar apogee, while the equinox observations led a pretty exact value for the length of the solar year.[25] Observations, which gave new values for the inclination of the ecliptic at 23⁰33',[26] the position of the solar apogee at 82⁰39',[27] and addressed  problems such as the rate of equinoctial precession, the mean motions of the sun, the moon and the planets and so on.[28] The precession was found to be one degree in sixty years and eight months.[29] Following the time of Al-Mamun, in good Islamic tradition, the Banu Musa Brothers, Habash, Al-Nayziri and al-Mahani  all checked the value of this constant through their observations.[30]

Making these observations possible, and yielding such results is largely due to the fact that at this early stage, already, large instruments were introduced. In this respect, Hartner corrects the prevailing view such as held by Neugebauer that colossal observational instruments were only known at the end of Islamic civilisation (14^th-15^th  century).[31] Such instruments, Hartner insists, were already in use in both Baghdad  and Damascus .[32] Al-Biruni , for instance, speaks of a quadrant that had an inner radius(?) of about five meters; that was made of marble and had an accessory part sliding over its arc, with a hole, through which one looked at the Sun and the spike located at the centre of the quadrant.[33] Montucla mentions a 52 foot instrument used in Damascus, which he guesses to be a gnomon.[34]

Another major breakthrough is the length of time devoted to observation from any one place. The Amajurs, thus, performed observations which stretched over nearly fifty years, including observations of fixed stars, as well as lunar, solar, and planetary observations, which resulted in the preparation of several astronomical tables.[35]

With the end of the 10^th century, Sayili observes, there came about a new stage in the history of observatories, with further advances: in administration, a legal status for the institution, involvement of more specialised staff, and better and larger instruments.[36] Rulers also played a more substantial role, the observatory in its ideal form becoming a royal institution.[37] Thus, in relation to instruments, Abu’l-Wafa (940-998) who worked at the observatory of the ruler Sharaf al-Daula, made observations using a 20 ft quadrant and a 56 ft stone sextant, and a wall quadrant, which he built himself for observing the stars.[38] At Shiraz, in the year 969, Al-Sufi was asked by Adud al-Dawla to measure the obliquity of the ecliptic, an operation done with the help of a ring several meters in diameter.[39] In the meantime, at Khwarizm, Al Biruni was engaged in observations of lunar eclipses using equally large instruments.[40]

A century or so after, an observatory was built by the Seljuk Sultan Malik Shah (ruled 1072-1092), in Ispahan.[41] There, he gathered together a large group of the most distinguished astronomers, amongst whom were al-Khayyami, Abu’l Muzaffer and Al-Wasiti.[42] An enormous amount of money was spent for the purpose, and the observation lasted for over thirty years.[43] The instruments used were much bulkier than before, the aim being to minimise error as much as possible.[44] Each piece was also dedicated to a particular class of observations.[45] Haji Khalifa, on the authority of Abd al-Wajid speaks of the Zij Malikshah by Umar Khayyam.[46] Qutb al-Din al-Shirazi, too, mentions Umar Khayyam’s zij.[47]

In this high medieval period, there also seems to be observation made in the Muslim west. Johnson speaks of observatories at Cordova, Seville , and Toledo , and also in Morocco , and describes them as intensely active.[48] There is reference to an observatory in Seville, or more precisely to the tower used by Jabir Ibn Aflah. This lofty tower was the minaret of the Friday mosque of Seville, later to be transformed into the famed Giralda Tower. Aschbach and Mamuni speak of this place as the first observatory built in Europe.[49]

In North Africa , the Star Tower was located in the city of Fes , and was used for observations of the new moon. This tower is said to have been in existence in the 12^th century and to have remained in existence for centuries after.[50] Special openings were provided on its top, serving as guides indicating the directions of observation for various months.[51] Al-Mamuni cites an unpublished source which contains information concerning this tower.[52] Al-Mamuni also mentions a later source indicating that the tower remained standing for a considerable length of time.[53]

In the 13^th century the largest and most advanced observatory to date was built at Maragha in Azerbaijan; the only contribution by the Mongols to learning, although that was far from being their aim, Hulagu, the observatory’s sponsor, being only interested in the star signs to carry out his wars on Islam. He employed Nasir Eddin at Tusi as astrologer, Nasir Eddin having advised Hulagu to carry the onslaught on Baghdad  in 1258.[54] The observatory was situated on a hill near to the town of Maragha, the imposing building occupying an esplanade of some 150 by 350 metres, and included a dome with a hole in the top to allow the sun's rays to pass. Maragha had a library of 40,000 volumes,[55] and its instruments, including quadrants, armillaries, astrolabes, were all designed and constructed at the site.[56]  The instruments made of rings had special purposes: ecliptical, solstitial and equatorial armillaries; a meridian armillary consisted of a graduated bronze ring in the shape of an alidade set upon the meridian to measure solar altitudes in zenith distance; a large stone sundial accurately aligned to the meridian and used only for determining the obliquity of the ecliptic; an equatorial armillary made in the form of a bronze ring set firmly parallel to the plane of the equator; and a parallactic instrument, a type of transit used to measure the zenith distance of a star or the moon at culmination.[57] Twelve years of observations and calculations at Maragha resulted in the Ilkhanide tables in 1271. Before then, on the 8^th of September 1264, the astronomers at Maragha observed the maximum height of the sun on the meridian and found it to be 55⁰ 29';[58] on 26^th October, it was 37⁰ 35'; on 5^th March 1265, it was 49⁰ 36' 30''.[59] The Maragha observatory survived for a few decades till the beginning of the 14^th century.[60]

The Samarkand  observatory, dating from 1424, was the accomplishment of Uluh Beg (1394-1449); a prince keen on the sciences, who also enjoyed the company of, and discussions with scholars.[61] The observatory of Samarkand was a ‘monumental' building equipped with a huge meridian, made of masonry, a symbol of the observatory meant as a long lasting institution.[62] It was equipped with a ‘Fakhri sextant’, of a radius of 40.4 metres. John Greaves writing in 1652 says that, according to a trustworthy Turkish  astronomer, the radius of that meridian arc was about equal to the height of the dome of the Ayasofya Mosque  in Istanbul,[63] thus, approximately fifty metres. Al-Birjandi states that the astronomers measured the obliquity of the ecliptic with the help of the suds-i-Fakhri.[64] The instruments mentioned by al-Khashi are a parrallactic ruler, armillary sphere, equinoctial armilla, the two ring Suds-i-Fakhri, azimuthal quadrant, the sine and versed sine instruments, the small armillary sphere (with four rings).[65] Al-Kashi (1380-1429), a very able astronomer and also the author of the finest eastern treatise on arithmetic, headed the staff,[66] which involved more than 100 scientists.[67]

Samarkand , in the early decades of the 15^th century, Krisciunas insists, was ‘the astronomical capital of the world.’[68] Observations were made there for almost three decades, and resulted in 1437 in the Ilkhanide Tables, of which a hundred copies still exist.[69] These included some excellent sine and tangent tables as well as improved planetary parameters and star positions. An unusually large number of these were based on original observations rather than on mere updating of Ptolemy or al-Sufi.[70]  Calculations helped devise a catalogue of 1012 stars, and measure the solar year to 365 days, 6 hours, 10 minutes and 8 seconds.[71] The star catalogue later aroused much interest in Europe, especially in the early days of serious Islamic studies in the early 17^th century.[72] The observatory at Samarkand remained active until nearly 1500,[73] before being brought down following political upheavals in the region. Its remains from 1908 yielded a fragment of the gnomon used to determine the height of the sun from the length of the shadow. There were also remains of a building of cylindrical shape with a complex interior plan.[74] Among the remains was a portrayal of the ten celestial spheres with degrees, minutes, seconds and tenths of seconds, the seven moving planets, fixed stars and the terrestrial sphere etc.[75]

Krisciunas insists that in the Samarkand  observatory the role of permanently mounted astronomical instruments was understood. So was the systematic basis of observation, for lengthy periods of time, 17 years or more of the same phenomena being pursued.[76] Ten or fifteen years were required due to conditions suited to the determination of matters pertaining to the planets, making it necessary to observe them only when such conditions were present, Krisciunas explains.[77] In his letter to his father, the astronomer al-Kashi writes:

‘As to the inquiry of those who ask why observations are not completed in one year but require ten to fifteen years, the situation is that there are certain circumstances suited for the determination of matters pertaining to the planets, and that they should be observed when these conditions obtain. One needs,  e.g., to have two eclipses in both of which the eclipsed parts are equal and on the same side, and both these eclipses have to be near the same node. Likewise, two other eclipses conforming to other specifications are needed, and still other cases of a similar nature are required. It is necessary to observe Mercury at a time when it is at its maximum morning elongation and once at its maximum evening elongation, in addition to certain other conditions, and a similar situation exists for the other planets.

‘Now, all these circumstances are not met within a single year, so that their observations cannot be completed in one year. It is necessary to wait until the required circumstances obtain, and then if there is cloud at the awaited time, the opportunity is lost and gone, and it is necessary to wait for another year or two for the repetition of the needed circumstances. Ten or fifteen years are required for this reason.’[78]

It also takes Saturn 29 years to return to the same position amongst the stars (that being its period of revolution about the Sun), and a period of 29 years might have been the projected length of the Samarkand  program of observations.[79]

Islamic observatories were the forerunners of modern observatories, whether with regard to their organisation, the instruments and methods used, the objectives assigned for each astronomer or observation, state involvement, etc. One major innovation was the tendency to narrow branches of specialisation, and to involve large groups of scholars in common endeavours. There were thus, calculators, arithmeticians, geometers, astronomers, astrologers, observers and instrument designers who were specialised in their own branch  of knowledge only.[80] The use and manipulation of astronomical instruments necessitated working in groups of observers, so that, in this case at least, the collaboration of astronomers of the same specialisation was also required.[81] That the foundation and functioning of the Islamic observatory was dependent upon the cooperation of many scientists is clearly stated by Islamic writers.[82] The emphasis upon astronomical work and observation in groups seems to explain the sudden appearance of impressive staffs in Islam in the observatories.[83] Hartner insists that it was only in the 17^th century, thanks to Brahe, that high standards of Islamic observation were reached again by the Europeans.[84]