Everything about Islamic Astronomy totally explained
In the
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-16th centuries), and mostly written in the
Arabic language. These developments mostly took place in the
Middle East,
Central Asia,
Al-Andalus,
North Africa, and later in
China and
India. It 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. These included
Indian,
Sassanid and
Hellenistic works in particular, which were translated and built upon. and
European
A significant number of
stars in the
sky, such as
Aldebaran and
Altair, and astronomical terms such as
alhidade,
azimuth, and
almucantar, are still today recognized with
their Arabic names.
A large corpus of literature from Islamic astronomy remains today, numbering approximately 10,000 manuscripts scattered throughout the world, many of which have not been read or cataloged. Even so, a reasonably accurate picture of Islamic activity in the field of astronomy can be reconstructed.
Islam and astronomy
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. On the basis of this advice Muslim began to find better observational and navigational instruments, thus most navigational stars today have Arabic names. in contrast to ancient
Greek philosophers such as the
Platonists and
Aristotelians who expressed a general distrust towards the
senses 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:
cosmological verses in the
Qur'an (610-632) which some modern writers have interpreted as foreshadowing the
expansion of the universe and possibly even the
Big Bang theory:
Don't those who reject faith see that the heavens and the earth were a single entity then We ripped them apart?
And the heavens We did create with Our Hands, and We do cause it to expand.
Several
hadiths attributed to
Muhammad also show that he was generally 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:
"An eclipse is a phenomenon of nature. It is foolish to attribute such things to the death or birth of a human being."
Islamic rules
There are several rules in Islam which lead Muslims to use better astronomical calculations and
observations.
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's the straight usage."
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.
Muslims are also expected to pray towards the
Kaaba in
Mecca and orient their
mosques in that direction. Thus they need to determine the direction of Mecca from a given location. Another problem is the time of
Salah. Muslims need to determine from
celestial bodies the proper times for the prayers at
sunrise, at
midday, in the
afternoon, at
sunset, and in the
evening.
Necessity of spherical geometry
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 fairly sophisticated
spherical geometry. Finding the direction of
Mecca and the time of
Salah are the reasons which led to Muslims developing 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
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 (the
arc through the zenith and the pole) and the sun's hour circle (the arc through the sun and the pole). 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,
Sassanid and
Hellenistic works which were
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:
700-825
This period was most notably the period of assimilation and syncretisation 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,
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.
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. 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 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.
Fragments of text during this period indicate that Arabs adopted the
sine function (inherited from
Indian trigonometry) instead of the
chords of
arc used in Hellenistic mathematics.
Islamic interest in
astronomy ran parallel to the interest in mathematics. Especially noteworthy in this regard was the
Almagest (c. 150) of the
Egyptian astronomer
Ptolemy (c. 100-178). The
Almagest was a landmark work in its field, assembling, as
Euclid's
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 translation,
Almagest. 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 and
Copernican Revolution. 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
sidereal phenomena. He drew up a list of chronological tables of
Assyrian,
Persian,
Greek, and
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 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
financially, but endowed the work with formal prestige.
Observational astronomy
In
observational astronomy, the first major original Muslim work of astronomy was
Zij al-Sindh by
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.
In 850,
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 obliquity of the ecliptic, the precessional movement of the
apogees 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.
Muhammad ibn Jābir al-Harrānī al-Battānī (Albatenius) (853-929) discovered that the direction of the Sun's
eccentric was changing, which in modern astronomy is equivalent to the Earth moving in an
elliptical orbit around the Sun. His times for the
new moon, lengths for the
solar year and
sidereal year, prediction of
eclipses, and work on the phenomenon of
parallax, carried astronomers "to the verge of
relativity and the
space age." 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.
In the 10th century,
al-Sufi (Azophi) carried out observations on the
stars and described their
positions,
magnitudes, brightness, and
colour, and drawings for each constellation in his
Book of Fixed Stars.
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 metres. His observations on
eclipses 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's.
Abu-Mahmud al-Khujandi relatively accurately computed the
axial tilt to be 23°32'19" (23.53°), which was a significant improvement over the Greek and Indian estimates of 23°51'20" (23.86°) and 24°, and still very close to the modern measurement of 23°26' (23.44°).
In 1006, the
Egyptian 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
St. Gall later corroborated bin Ridwan's observations as to magnitude and location in the sky.
Early heliocentric models
In the late ninth century,
Ja'far ibn Muhammad Abu Ma'shar al-Balkhi developed a planetary model which some have interpreted as a
heliocentric model. This is due to his
orbital revolutions of the planets being given as heliocentric revolutions rather than
geocentric revolutions, and the only known planetary theory in which this occurs is in the heliocentric theory. His work on planetary theory hasn't survived, but his astronomical data was later recorded by al-Hashimi,
Abū Rayhān al-Bīrūnī and
al-Sijzi.
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:
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 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:
Indica, al-Biruni briefly refers to his work on the refutation of heliocentrism, the
Key of Astronomy, which is now lost:
In his
Astral Motion and
The Force of Attraction, Muhammad ibn Musa proposed that there was a
force of
attraction between
heavenly bodies, foreshadowing
Newton's law of universal gravitation.
Ibn al-Haytham (Alhacen), in his
Book of Optics (1021), was the first to discover that the
celestial spheres don't 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 and
Tychonic systems of astronomy.
Beginning of experimental astronomy
In the tenth century,
Muhammad ibn Jābir al-Harrānī al-Battānī (Albatenius) (853-929) introduced the idea of
testing "past observations by means of new ones". This led to the use of exacting
empirical observations and experimental techniques by Muslim astronomers from the eleventh century onwards.
In the eleventh century,
Abū Rayhān al-Bīrūnī introduced the
experimental method into astronomy and was the first to conduct elaborate
experiments related to astronomical phenomena. 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
latitudes of the stars during the lunar eclipse.
1025-1450
During this period, a distinctive Islamic system of astronomy flourished. Within the Greek tradition and its successors it was traditional 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
mathematical and
physical principles. Within the context of this
hay'a tradition, Muslim astronomers began questioning technical details of the
Ptolemaic system of astronomy. Most of these criticisms, however, continued to follow the Ptolemaic astronomical
paradigm, remaining within the
geocentric framework. As the historian of astronomy,
A. I. Sabra, noted:
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. Several other Muslim astronomers, most notably those following the
Maragha school of thought, developed non-Ptolemaic planetary models within a geocentric context that were later adapted in the
Copernican model in a
heliocentric context.
Refutations of astrology
The first
semantic distinction between astronomy and
astrology was given by the
Persian astronomer
Abu Rayhan al-Biruni in the 11th century, 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 both due to the methods used by astrologers being
conjectural rather than
empirical and also due to the views of astrologers conflicting with orthodox
Islam.
Astrophysics and celestial mechanics
In
astrophysics and
celestial mechanics,
Abū Rayhān al-Bīrūnī described the Earth's
gravitation as:
In 1121,
al-Khazini, in his treatise
The Book of the Balance of Wisdom, states:
Al-Khazini was thus the first to propose the theory that the
gravities of bodies vary depending on their distances from the centre of the Earth. This phenomenon wasn't proven until
Newton's law of universal gravitation in the 18th century. and for relating actual physical motions to imaginary mathematical points, lines and circles:
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. In his
Epitome of Astronomy, he insisted that the heavenly bodies "were accountable to the
laws of physics." The foundations of
telescopic astronomy can also be traced back to Ibn al-Haytham, due to the influence of his
optical studies on the later development of the modern telescope.
In 1038, Ibn al-Haytham described the first non-Ptolemaic configuration in
The Model of the Motions. His reform wasn't concerned with
cosmology, as he developed a systematic study of celestial
kinematics that was completely
geometric. This in turn led to innovative developments in
infinitesimal geometry. His reformed model was the first to reject the
equant and
eccentrics, 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, and the centres of motion were geometrical points without any physical significance, like
Johannes Kepler's model centuries later. 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
cosmological hypotheses that can't be observed from
Earth.
Early alternative models
In 1030,
Abū al-Rayhān al-Bīrūnī discussed the
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 rotates on its axis and Biruni noted that this doesn't create any mathematical problems.
Abu Said
al-Sijzi, a contemporary of al-Biruni, suggested the possible heliocentric movement of the Earth around the Sun, which al-Biruni didn't reject. Al-Biruni agreed with the
Earth's rotation about its own axis, and while he was initially neutral regarding the
heliocentric and
geocentric models, he considered heliocentrism to be a philosophical problem.
In 1031, al-Biruni completed his extensive astronomical encyclopaedia
Kitab al-Qanun al-Mas'udi (
Latinized as
Canon Mas’udicus), 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. The book introduces the mathematical technique of analysing the
acceleration of the planets, and first states that the motions of the
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 the annual
solar eclipses.
In 1070,
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.
Andalusian Revolt
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
Ptolemaic model. 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".
In the late 11th century,
al-Zarqali (Latinized as Arzachel) discovered that the orbits of the planets are
elliptic orbits and not circular orbits, though he still followed the Ptolemaic model.
In the 12th century,
Averroes rejected the
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:}}
Later in the 12th century, Ibn Bajjah's successors,
Ibn Tufail (Abubacer) and
al-Betrugi (Alpetragius), were the first to propose planetary models without any
equant,
epicycles or eccentrics. Al-Betrugi was also the first to discover that the planets are
self-luminous. 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, mainly because they followed
Aristotle's notion of perfect circular motion.
Maragha Revolution
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
Damascus and
Samarkand. 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 observations. The most important of the Maragha astronomers included
Mo'ayyeduddin Urdi (d. 1266),
Nasīr al-Dīn al-Tūsī (1201-1274), 'Umar al-Katibi al-
Qazwini (d. 1277),
Qutb al-Din al-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).
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 behaviour of
physical bodies in
mathematical language, and shouldn't remain a mathematical
hypothesis, which would only save the
phenomena. The Maragha astronomers also realized that the
Aristotelian view of
motion in the universe being only circular or
linear wasn't true, as the
Tusi-couple showed that linear motion could also be produced by applying
circular motions only.
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 mathematics with the real world surrounding them, 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
Aristotelian cosmology and
Ptolemaic astronomy and towards a greater emphasis on the empirical observation and
mathematization of astronomy and of
nature in general, as exemplified in the works of Ibn al-Shatir, al-Qushji, al-Birjandi and al-Khafri.
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, the rejection of the Ptolemaic model on empirical rather than
philosophical grounds by Ibn al-Shatir,
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".
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, and conceived a plausible model for
elliptical orbits. His work thus marked a turning point in astronomy, which may be considered a "Scientific Revolution before the Renaissance". In the published version of his masterwork,
De revolutionibus orbium coelestium, Copernicus also cites the theories of
al-Battani,
Arzachel and
Averroes as influences,
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. Ali al-Qushji also improved on al-Tusi's planetary model and presented an alternative planetary model for
Mercury.
In the 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 rotating, develops a hypothesis similar to
Galileo Galilei's notion of "circular
inertia", which he described in the following observational test (as a response to one of
Qutb al-Din al-Shirazi's arguments):
Theoretical astronomy
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, after
George Saliba studied the works of a 16th century astronomer, Shams al-Din al-Khafri (d. 1550), a
Safavid commentator on earlier
Maragha astronomers. Saliba wrote the following on al-Khafri's work:
Observational astronomy
Another notable 16th century Muslim astronomer was the
Ottoman astronomer
Taqi al-Din, who built the
Istanbul observatory of al-Din in 1577, where he carried out astronomical observations until 1580. He produced a
Zij (named
Unbored Pearl) and
astronomical catalogues 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 point notation in his
observations rather than the
sexagesimal fractions used by his contemporaries and predecessors. After the destruction of the Istanbul observatory of al-Din in 1580, however, 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.
Meanwhile 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
Hindu computational techniques. While there appears to have been little concern for theoretical astronomy, Muslim and
Hindu astronomers in
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 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 techniqes from the Hindu tradition. In particular, one of the most remarkable astronomical instruments invented by Muslims in Mughal India is the seamless celestial globe (see
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 didn't interest them at the time.
1900-present
In the 20th and 21st centuries, Muslim astronomers have been making advances in moon sighting, while Muslim
astronauts and
rocket scientists have been involved in research on
astronautics and
space exploration.
Muslim participation in astronautics and space exploration
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
human spaceflight (
Vostok 1), and responsible for the launch of the first
space stations (the
Salyut and
Mir series) as well as their predecessors (the
Cosmos 186 and
Cosmos 188).
Farouk El-Baz from
Egypt worked for the rival
NASA and was involved in the first
Moon landings 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.
In the late 20th and early 21st centuries, there have also been a number of Muslim astronauts, 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
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 travelled 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
prayer in a low-gravity environment, the location of
Mecca from ISS, determination of prayer times, and issues surrounding
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 crystallisation of various
proteins and
microbes in space.
Other prominent Muslim scientists involved in research on the
space sciences 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.
New efforts in moon sighting
According to Islam, Muslims should observe religious duties during special days on the basis of the
Islamic lunar calendar. Therefore, moon sighting is an important issue for Muslims. 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 and new
religious questions have emerged.
In 2005,
Ayatollah Ali Khamenei,
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.
Ayatollah Khamenei has established a Moon Observation Committee, comprised of
clerics who pore over sightings reported to centers. Scientists note the moon's angle, position, and illumination, and compare the sightings from the field with
computerized
charts 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
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
mapmakers 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.
Observatories
The modern astronomical
observatory as a
research institute was 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,
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.
Early observatories
The first systematic observations in Islam 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 degrees were measured, solar parameters were established, and detailed observations of the
Sun,
Moon, and
planets were undertaken.
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 o-dowleh, who systematically revised
Ptolemy's catalogue of
stars.
Sharaf al-Daula also established a similar observatory in
Baghdad. And reports by
Ibn Yunus and
al-Zarqall in
Toledo and
Cordoba indicate the use of sophisticated instruments for their time.
It was
Malik Shah I who established the first large observatory, probably in
Isfahan. It was here where
Omar Khayyám with many other collaborators constructed a
zij and formulated the
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.
Late medieval observatories
The more influential observatories, however, 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.
In 1420, prince
Ulugh Beg, himself an astronomer and mathematician, founded another large observatory in
Samarkand, the remains of which were excavated in 1908 by Russian teams. In 1577,
Taqi al-Din bin Ma'ruf founded the large
Istanbul observatory of al-Din, which was on the same scale as those in Maragha and Samarkand.
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 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 techniqes from the Hindu tradition.
Palestine,
Lebanon,
UAE,
Tunisia, 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 metre
telescope observatory in the near future.
Instruments
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 made many improvements to instruments already in use before their time, such as adding new scales or details, and invented many of their own new instruments. Their contributions to astronomical instrumentation are abundant. Many of these instruments were often invented or designed for
Islamic purposes, such as the determination of the direction of
Qibla or the times of
Salah.
Astrolabes
Brass
astrolabes were developed in much of the
Islamic world, often as an aid to finding the
qibla. The
earliest known example
is dated 315 (in the
Islamic calendar, corresponding to 927-8CE). The first person credited for building the Astrolabe in the Islamic world is reportedly
Fazari. Though the first primitive astrolabe to chart the stars was invented in the
Hellenistic civilization, al-Fazari made several improvements to the device. 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.
Large astrolabe
Ibn Yunus 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 metres.
Navigational astrolabe
The first navigational astrolabe was invented in the Islamic world during the Middle Ages, and employed the use of a polar projection system.
Orthographical astrolabe
Abu Rayhan al-Biruni invented and wrote the earliest treatise on the orthographical astrolabe in the 1000s.
Astrolabic clock
Ibn al-Shatir invented the astrolabic clock in 14th century Syria.
Analog computers
Various
analog computer devices were invented to compute the
latitudes of the Sun, Moon, and planets, the
ecliptic of the Sun, the time of day at which
planetary conjunctions 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 longitudes and positions of the Moon, Sun, and planets, without calculation using a geometrical model to represent the celestial body's mean and anomalistic position.
Planisphere and mechanical geared calendar computer
Abū Rayhān al-Bīrūnī invented and wrote the earliest treatise on the planisphere, an analog computer, in the 1000s. This was an early example of a fixed-wired knowledge processing machine.
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 systems. It was designed to take and convert measurements made in three sets of coordinates: horizon, equatorial, and ecliptic.
Mechanical astrolabe with geared calendar computer
In 1235, Abi Bakr of Isfahan invented a brass astrolabe with a geared calendar movement based on the design of Abū Rayhān al-Bīrūnī's mechanical calendar computer. Abi Bakr's geared astrolabe uses a set of gear-wheels and is the oldest surviving complete mechanical geared machine in existence.
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 conjunctions will occur, and for performing linear interpolation. and the planets in terms of elliptical orbits; the latitudes of the Sun, Moon, and planets; and the ecliptic of the Sun. The instrument also incorporated an alhidade and ruler.
Astronomical clocks
The Muslims constructed a variety of highly accurate
astronomical clocks for use in their observatories.
Water-powered astronomical clocks
Al-Jazari invented monumental water-powered astronomical clocks which displayed moving models of the Sun, Moon, and stars. His largest astronomical clock displayed the zodiac and the solar and lunar orbits. Another innovative feature of the clock was a pointer which traveled across the top of a gateway and caused automatic doors to open every hour.
Mechanical observational clock
Taqi al-Din invented the "observational clock", which he described as "a mechanical clock with three dials which show the hours, the minutes, and the seconds." He used this for astronomical purposes, specifically for measuring the right ascension of the stars. 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. Muslim astronomers and engineers were the first to write instructions on the construction of horizantal sundials, vertical sundials, and polar sundials.
Navicula de Venetiis
This was a universal horary dial invented in 9th century Baghdad. It was used for accurate timekeeping by the Sun and Stars, and could be observed from any latitude. This was later known in Europe as the "Navicula de Venetiis", which was considered the most sophisticated timekeeping instrument of the Renaissance.
Globes
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
The spherical astrolabe was first produced in the Islamic world. It was an Islamic variation of the astrolabe and the armillary sphere, of which only one complete instrument, from the 14th century, has survived.
Celestial globes
Celestial globes 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 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."
Seamless celestial globe
The 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 globes 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 . 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.
Mural instruments
A number of
mural instruments (including several different
quadrants and
sextants) were invented by Muslim astronomers and engineers.
Sine quadrant
The sine quadrant, invented by Muhammad ibn Mūsā al-Khwārizmī in 9th century Baghdad, was used for astronomical calculations.
Quadrans Novus
Quadrans Vetus was a universal horary quadrant, an ingeniuous mathematical device invented by al-Khwarizmi in 9th century Baghdad and 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.
Quadrans Vetus
The astrolabic quadrant was invented in Egypt in the 11th century or 12th century, and later known in Europe as the "Quadrans Vetus" (New Quadrant).
Almucantar quadrant
The first almucantar quadrant was invented in the medieval Islamic world, and it employed the use of trigonometry. The term "almucantar" is itself derived from Arabic. The Almucantar quadrant was originally modified from the astrolabe. 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.
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's "dedicated to verifying the presence of the new cresent on the horizon." Though these early observation tubes didn't have
lenses, they "enabled an observer to focus on a part of the sky by eliminating
light inteference." These observation tubes were later adopted in
Latin-speaking Europe, where they influenced the development of the
telescope.
Other instruments
Various other astrononmical instruments were also invented in the Islamic world:
The first astronomical uses of the magnetic compass is found in a treatise on astronomical instruments written by the Yemeni sultan al-Ashraf (d. 1296). This was the first reference to the compass in astronomical literature.
The Alhidade was invented in the Islamic world, while the term "alhidade" is itself derived from Arabic.
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.
In 17th century Safavid Persia, two unique brass instruments with Mecca-centred world maps engraved on them were produced primarily for the purpose of finding the Qibla. These instruments were engraved with cartographic 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. One of the two instruments, produced by Muhammad Husayn, also had a sundial and compass attached to it.
The shadow square was an instrument used to determine the linear height of an object, in conjunction with the alidade, for angular observations. It was invented by Muhammad ibn Mūsā al-Khwārizmī in 9th century Baghdad.
List of notable treatises
Zij treatises
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 (Latinized as Algorismi) (c. 780-850)
Muhammad ibn Jābir al-Harrānī al-Battānī (Latinized as Albategni) (853-929)
Abd Al-Rahman Al Sufi (Latinized as Azophi) (903-986)
Al-Zarqali (Latinized as Arzachel) (1028-1087)
Al-Khazini (fl. 1115-1130)
- Az-Zij as-Sanjarī (Sinjaric Tables) (1115-1116)
Nasīr al-Dīn al-Tūsī (1201-1274)
Jamshīd al-Kāshī (1380-1429)
Ulugh Beg (1394-1449)
Taqi al-Din (1526-1585)
- Unbored Pearl (1577-1580)
Almanacs
The word "Almanac" is an Arabic word. The modern almanac differs from earlier astronomical tables (such as the earlier 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 1088 by Abū Ishāq Ibrāhīm al-Zarqālī (Latinized as Azarqueil) in 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.
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 instruments: the triquetrum, dioptra, a triangular instrument he invented, the quadrant and sextant, the astrolabe, and original instruments involving reflection.
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.
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)
Abu Ubayd al-Juzjani (c. 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)
'Umar al-Katibi al-Qazwini (d. 1277)
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 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
Many of the modern names for numerous stars and constellations are derived from their Arabic language names. Examples include: Acamar, Aldebaran, Altair, Baham, 
