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Egyptian astronomy begins in prehistoric times, in the Predynastic Period. In the 5th millennium BCE, the stone circles at Nabta Playa made use of astronomical alignments. By the time the historical Dynastic Period began in the 3rd millennium BCE, the 365 day period of the Egyptian calendar was already in use, and the observation of stars was important in determining the annual flooding of the Nile. The Egyptian pyramids were carefully aligned towards the pole star, and the temple of Amun-Re at Karnak was aligned on the rising of the midwinter sun. Astronomy played a considerable part in fixing the dates of religious festivals and determining the hours of the night, and temple astrologers were especially adept at watching the stars and observing the conjunctions, phases, and risings of the Sun, Moon and planets. The ancient Egyptians also laid the foundations for theoretical astronomy, introducing the concept of a celestrial sphere.

In Ptolemaic Egypt, the Egyptian tradition merged with Greek astronomy and Babylonian astronomy, with the city of Alexandria in Lower Egypt becoming the centre of scientific activity across the Hellenistic world. In Roman Egypt, we find the greatest astronomer of the era, Ptolemy (90-168 CE). His works on astronomy, particularly the Almagest, became the most influential books in the history of Western astronomy. Following the Muslim conquest of Egypt, the region came to be dominated by Arabic culture and Islamic astronomy. The astronomer Ibn Yunus (c. 950-1009) observed the sun's position for many years using a large astrolabe, and his observations on eclipses were still used centuries later. In 1006, Ali ibn Ridwan observed the SN 1006, a supernova regarded as the brightest steller event in recorded history, and left the most detailed description of it. In the 14th century, Najm al-Din al-Misri wrote a treatise describing over 100 different types of scientific and astronomical instruments, many of which he invented himself. In Ottoman Egypt, Taqi al-Din invented the most accurate astronomical clock of the 16th century and built the Istanbul observatory where he produced a Zij and astronomical catalog that were more accurate than those of his contemporaries, Tycho Brahe and Nicolaus Copernicus.[1] In the 20th century, Farouk El-Baz from Egypt worked for NASA and was involved in the first Moon landing with the Apollo program, where he assisted in the planning of scientific explorations of the Moon.[2]

Ancient EgyptEdit

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Egyptian astronomy begins in prehistoric times. The presence of stone circles at Nabta Playa dating from the 5th millennium BCE show the importance of astronomy to the religious life of ancient Egypt even in the prehistoric period. The annual flooding of the Nile meant that the heliacal risings, or first visible appearances of stars at dawn, was of special interest in determining when this might occur, and it is no surprise that the 365 day period of the Egyptian calendar was already in use at the beginning of Egyptian history. The constellation system used among the Egyptians also appears to have been essentially of native origin.

The precise orientation of the Egyptian pyramids affords a lasting demonstration of the high degree of technical skill in watching the heavens attained in the 3rd millennium BCE. It has been shown the Pyramids were aligned towards the pole star, which, because of the precession of the equinoxes, was at that time Thuban, a faint star in the constellation of Draco.[3] Evaluation of the site of the temple of Amun-Re at Karnak, taking into account the change over time of the obliquity of the ecliptic, has shown that the Great Temple was aligned on the rising of the midwinter sun.[4] The length of the corridor down which sunlight would travel would have limited illumination at other times of the year.

Astronomy played a considerable part in religious matters for fixing the dates of festivals and determining the hours of the night. The titles of several temple books are preserved recording the movements and phases of the sun, moon and stars. The rising of Sirius (Egyptian: Sopdet, Greek: Sothis) at the beginning of the inundation was a particularly important point to fix in the yearly calendar..

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From the tables of stars on the ceiling of the tombs of Rameses VI and Rameses IX it seems that for fixing the hours of the night a man seated on the ground faced the Astrologer in such a position that the line of observation of the pole star passed over the middle of his head. On the different days of the year each hour was determined by a fixed star culminating or nearly culminating in it, and the position of these stars at the time is given in the tables as in the centre, on the left eye, on the right shoulder, etc. According to the texts, in founding or rebuilding temples the north axis was determined by the same apparatus, and we may conclude that it was the usual one for astronomical observations. In careful hands it might give results of a high degree of accuracy.

During the 2nd millennium BC, the ancient Egyptians also laid the foundations for theoretical astronomy, introducing the concept of a celestrial sphere. [1] This paved the way for the theoretical astornomical traditions that later developed in the Greek, Hellenistic and Islamic astronomical traditions.

Ambrosius Theodosius Macrobius (395–423 AD) attributed the planetary theory where the Earth rotates on its axis and the interior planets Mercury and Venus revolve around the Sun which in turn revolves around the Earth, to the ancient Egyptians. He named it the "Egyptian System," and stated that "it did not escape the skill of the Egyptians," though there is no other evidence it was known in ancient Egypt.[5][6]

Hellenistic EgyptEdit

See also: Babylonian astronomy

Writing in the Roman era, Clement of Alexandria gives some idea of the importance of astronomical observations to the sacred rites:

And after the Singer advances the Astrologer (ὡροσκόπος), with a horologium (ὡρολόγιον) in his hand, and a palm (φοίνιξ), the symbols of astrology. He must know by heart the Hermetic astrological books, which are four in number. Of these, one is about the arrangement of the fixed stars that are visible; one on the positions of the sun and moon and five planets; one on the conjunctions and phases of the sun and moon; and one concerns their risings.[7]

The Astrologer's instruments (horologium and palm) are a plumb line and sighting instrument. They have been identified with two inscribed objects in the Berlin Museum; a short handle from which a plumb line was hung, and a palm branch with a sight-slit in the broader end. The latter was held close to the eye, the former in the other hand, perhaps at arms length. The "Hermetic" books which Clement refers to are the Egyptian theological texts, which probably have nothing to do with Hellenistic Hermetism.[8]

Following Alexander the Great's conquests and the foundation of Ptolemaic Egypt, the native Egyptian tradition of astronomy had merged with Greek astronomy as well as Babylonian astronomy. The city of Alexandria in Lower Egypt became the centre of scientific activity throughout the Hellenistic civilization. The greatest Alexandrian astronomer of this era was Eratosthenes (c. 276-195 BCE), who calculated the size of the Earth, providing an estimate for the Earth radius.

Following the Roman conquest of Egypt, the region once again became the centre of scientific activity throughout the Roman Empire. The greatest astronomer of this era was the Hellenized Egyptian, Ptolemy (90-168 CE). Originating from the Thebaid region of Upper Egypt, he worked at Alexandria and wrote works on astronomy including the Almagest, the Planetary Hypotheses, and the Tetrabiblos, as well as the Handy Tables, the Canobic Inscription, and other minor works. The Almagest is one of the most influential books in the history of Western astronomy. In this book, Ptolemy explained how to predict the behavior of the planets with the introduction of a new mathematical tool, the equant.

A few mathematicians of late Antiquity wrote commentaries on the Almagest, including Pappus of Alexandria as well as Theon of Alexandria and his daughter Hypatia. Ptolemaic astronomy became standard in medieval European and Islamic astronomy until it was displaced by Maraghan, heliocentric and Tychonic systems by the 16th century.

Planetary models and observational astronomy Edit

In the 2nd century BC, Hipparchus, a Hellenistic astronomer who worked at Alexandria in Ptolemaic Egypt, aware of the extraordinary accuracy with which Babylonian astronomers could predict the planets' motions, insisted that Hellenistic astronomers achieve similar levels of accuracy. Somehow he had access to Babylonian observations or predictions, and used them to create better geometrical models. For the Sun, he used a simple eccentric model, based on observations of the equinoxes, which explained both changes in the speed of the Sun and differences in the lengths of the seasons. For the Moon, he used a deferent and epicycle model. He could not create accurate models for the remaining planets, and criticized other Greek astronomers for creating inaccurate models.

Hipparchus also compiled a star catalogue. According to Pliny the Elder, he observed a nova (new star). So that later generations could tell whether other stars came to be, perished, moved, or changed in brightness, he recorded the position and brightness of the stars. Ptolemy mentioned the catalogue in connection with Hipparchus' discovery of precession. (Precession of the equinoxes is a slow motion of the place of the equinoxes through the zodiac, caused by the shifting of the Earth's axis). Hipparchus thought it was caused by the motion of the sphere of fixed stars.

Ptolemaic astronomyEdit

Ptolemy was a Hellenized Egyptian astronomer and mathematician, who worked at Alexandria in Roman Egypt, in the 2nd century. Ptolemy's works on astronomy and astrology include the Almagest, the Planetary Hypotheses, and the Tetrabiblos, as well as the Handy Tables, the Canobic Inscription, and other minor works.

The Almagest is one of the most influential books in the history of Western astronomy. In this book, Ptolemy explained how to predict the behavior of the planets, as Hipparchus could not, with the introduction of a new mathematical tool, the equant. The Almagest gave a comprehensive treatment of astronomy, incorporating theorems, models, and observations from many previous mathematicians. This fact may explain its survival, in contrast to more specialized works that were neglected and lost. Ptolemy placed the planets in the order that would remain standard until it was displaced by the heliocentric system and the Tychonic system:

  1. Moon
  2. Mercury
  3. Venus
  4. Sun
  5. Mars
  6. Jupiter
  7. Saturn
  8. Fixed stars

The extent of Ptolemy's reliance on the work of other mathematicians, in particular his use of Hipparchus' star catalogue, has been debated since the 19th century. A controversial claim was made by Robert R. Newton in the 1970s. in The Crime of Claudius Ptolemy, he argued that Ptolemy faked his observations and falsely claimed the catalogue of Hipparchus as his own work. Newton's theories have not been adopted by most historians of astronomy.

A few mathematicians of Late Antiquity wrote commentaries on the Almagest, including Pappus of Alexandria as well as Theon of Alexandria and his daughter Hypatia. Ptolemaic astronomy became standard in medieval western European and Islamic astronomy until it was displaced by Maraghan, heliocentric and Tychonic systems by the 16th century. However, recently discovered manuscripts reveal that Greek astrologers of Antiquity continued using pre-Ptolemaic methods for their calculations (Aaboe, 2001).

Islamic EgyptEdit

See also: w:c:islam:Islamic astronomy and Islamic astronomy

Following the Muslim conquest of Egypt, the region came to be dominated by Arabic culture. It was ruled by the Rashidun, Umayyad and Abbasid Caliphates up until the 10th century, when the Fatimids founded their own Caliphate centred around the city of Cairo in Egypt. The region once again became a centre of scientific activity, competing with Baghdad for intellectual dominance in the medieval Islamic world. By the 13th century, the city of Cairo eventually overtook Baghdad as the intellectual center of the Islamic world.

Medieval eraEdit

Early observational astronomyEdit

Ibn Yunus (c. 950-1009) 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 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.[9]

In the 10th century, Al-Sufi first described over 1,000 different uses of an astrolabe, in areas as diverse as astronomy, astrology, horoscopes, navigation, surveying, timekeeping, Qibla, Salah, etc.[10]

In 1006, Ali ibn Ridwan observed the SN 1006, a supernova regarded as the brightest steller event in recorded history, and left the most 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.

Experimental astronomy, astrophysics, celestial mechanicsEdit

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 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 experimental 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 intensity of the light-spot formed by the projection of the moonlight through two small apertures onto a screen diminishes constantly as one of the apertures is gradually blocked up."[11]

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 and Tychonic systems of astronomy.[12]

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 region of the world which is continuous with the heavenly motions."[13] Ibn al-Haytham refuted this by making the first attempt at observing and measuring the Milky Way's parallax,[14] 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."[15]

Refutations of astrologyEdit

See also: Islamic astrology

The first semantic distinction between astronomy and astrology was given by the Persian astronomer Abu Rayhan al-Biruni in the 11th century,[16] 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 Islamic scholars) reasons.[17]

Hay'a programEdit

See also: Maragheh observatory and Zij-i Ilkhani
File:Ibn al-Haytham.png

Between 1025 and 1028, Ibn al-Haytham (Latinized 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, observational and experimental grounds,[18] and for relating actual physical motions to imaginary mathematical points, lines and circles:

"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."[19]

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.[20] In his Epitome of Astronomy, he insisted that the heavenly bodies "were accountable to the laws of physics."[21]

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 geometric. This in turn led to innovative developments in infinitesimal geometry.[22] His reformed model was the first to reject the equant[23] and eccentrics,[24] 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,[25] and the centres of motion were geometrical points without any physical significance, like Johannes Kepler's model centuries later.[26] 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 cannot be observed from Earth.[27]

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.[28] Al-Biruni agreed with the Earth's rotation about its own axis, and while he was initially neutral regarding the heliocentric and geocentric models,[29] he considered heliocentrism to be a philosophical problem.[30] He remarked that if the Earth rotates on its axis and moves around the Sun, it would remain consistent with his astronomical parameters:[31][32]

"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 (Latinized as Canon Mas’udicus),[33] 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.[34] 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 annular eclipses.[31][35]

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.[36] 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".[37]

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 Damascus mosque and 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 observations.[38] 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).[39]

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".[40] 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,[41] and conceived a plausible model for elliptical orbits.[33] 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. 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.[28]

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 solar model and all the eccentrics, epicycles and equant in the Ptolemaic lunar model. His model was thus in better agreement with empirical observations than any previous model,[38] and was also the first that permitted empirical testing.[42] His work thus marked a turning point in astronomy, which may be considered a "Scientific Revolution before the Renaissance".[38] His rectified model was later adapted into a heliocentric model by Copernicus,[41] which was mathematically achieved by reversing the direction of the last vector connecting the Earth to the Sun.[30] In the published version of his masterwork, De revolutionibus orbium coelestium, Copernicus also cites the theories of al-Battani, Arzachel and Averroes as influences,[33] while the works of Ibn al-Haytham and al-Biruni were also known in Europe at the time.

InstrumentsEdit

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.[43]

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 AH, (927/8 CE). The first person credited for building the Astrolabe in the Islamic world is reportedly Fazari.[44] 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,[45] adding circles indicating azimuths on the horizon.[46] 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.[10]

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.[47] The almucantar quadrant was originally modified from the astrolabe.[48] It was invented in Egypt in the 11th or 12th century, and was later known in Europe as the "Quadrans Vetus" (New Quadrant).[49] It was intended as a simplified alternative to the astrolabe serving a specific latitude. According to David King:[50]

"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."
Sine quadrant

The sine quadrant, invented by Muhammad ibn Mūsā al-Khwārizmī in 9th century Baghdad, was used for astronomical calculations.[51] 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.[52]

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.[51]

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.[52] The Shakkaziya quadrant produced by Jamal al-Din al-Maridini was an analog computer for solving problems of spherical astronomy.[53] By the time of the Mamluk Sultanate, Muslim astronomers "developed the quadrant to all conceivable limits; it virtually replaced the astrolabe in Syria and Egypt in Mamluk and Ottoman times."[50]

Sundials

Muslims made several important improvements to the theory and construction of sundials, which they inherited from their Indian and 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 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.[54] Muslim astronomers and engineers were the first to write instructions on the construction of horizontal sundials, vertical sundials, and polar sundials.[48]

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.[55][56]

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 experimental device" showing "that the intensity of the light-spot formed by the projection of the moonlight through two small apertures onto a screen diminishes constantly as one of the apertures is gradually blocked up."[11]

Magnifying lens

The first optical research to describe a magnifying lens used in an instrument was found in a book called the Book of Optics (1021) written by Ibn al-Haytham (Alhazen).[57] His descriptions were fundamental to the development of the telescope and helped set the parameters in Europe for the later advances in telescopic technology.[58] His additional work in light refraction, parabolic mirrors, as well as the creation of other instruments such as the camera obscura, also helped spark the Scientific Revolution.[57][59]

Other worksEdit

  • 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)
  • Al-Istidrak ala Batlamyus (Recapitulation regarding Ptolemy) (11th century)
  • Ibn al-Shatir (1304–1375)
    • A Final Inquiry Concerning the Rectification of Planetary Theory

Influence in Christian EuropeEdit

File:Astrolabe quadrant England 1388.jpg
See also: Islamic contributions to Medieval Europe and Latin translations of the 12th century

During this period, Islamic-ruled regions of Europe, such as Al-Andalus, the Emirate of Sicily, and southern Italy, were slowly being reconquered by Christians. This led to the Arabic-Latin translation movement, which saw the assimilation of knowledge from the Islamic world by Western European science, including astronomy.[30]

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,[60] Ahmad ibn Muhammad ibn Kathīr al-Farghānī's On Elements of Astronomy on the Celestial Motions,[61] the works of Thabit ibn Qurra and Hunayn ibn Ishaq,[62] 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).[9] The astronomical works translated by Plato of Tivoli included Al-Battani's astronomical and trigonometrical work De motu stellarum. Al-Khwarizmi's Astronomical tables (also containing trigonometric tables) were translated by Robert of Chester[60] and by Adelard of Bath (fl. 1116-1142), who also translated the Introduction to Astrology of Abū Ma'shar.[63] Adelard associated with other scholars in Western England such as Peter Alfonsi and Walcher of Malvern who translated and developed the astronomical concepts brought from Islamic Spain.[64] Other Arabic astronomical texts translated into Latin include Muhammad al-Fazari's Great Sindhind (based on the Surya Siddhanta and the works of Brahmagupta).[65]

Ottoman eraEdit

See also: Science and technology in the Ottoman Empire

In Ottoman Egypt, the most notable astronomer was Taqi al-Din Muhammad ibn Ma'ruf. In 1577, he built the Istanbul observatory of Taqi al-Din 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.[1] He also invented a variety of astronomical instruments, including a framed sextant and several accurate mechanical astronomical clocks from 1556 to 1580, such as a mechanical alarm clock[66] and a mechanical astronomical clock that measured time in seconds and was the most accurate clock of the 16th century. The latter is considered one of the most important innovations in 16th-century practical astronomy, as at the beginning of the century, clocks were not accurate enough to be used for astronomical purposes.[1]

Earlier in 1574, Taqi al-Din used astrophysics to explain the intromission model of vision. He stated since the stars 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."[67]

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.[68]

Spring-powered astronomical clock

Taqi al-Din invented the first astronomical clock to be powered by springs, first described in his The Brightest Stars for the Construction of Mechanical Clocks (1556–1559).[69]

Mechanical alarm clock

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 wheel to when one wants the alarm heard and by producing an automated ringing device at the specified time.[69]

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." 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 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.[1] 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."[70]

Telescope

Taqi al-Din describes a long-distance 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.[67]

Framed sextant

At the Istanbul observatory of Taqi al-Din between 1577 and 1580, Taqi al-Din invented the mushabbaha bi'l manattiq, a framed sextant with cords for the determination of the equinoxes similar to what Tycho Brahe later used.[1]

Modern eraEdit

In the 20th century, Farouk El-Baz from Egypt worked for 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.[2]

In 2012, the 19 year-old Muslim female Egyptian physicist, Aisha Mustafa, invented a spacecraft propulsion method to propel spacecraft using quantum mechanics, allowing greater efficiency and faster space travel than the ordinary rocket engines currently used for spacecraft. [2]

See alsoEdit

NotesEdit

  1. 1.0 1.1 1.2 1.3 1.4 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.
  2. 2.0 2.1 "Muslim Scientists and Space Exploration - Farouk El-Baz: With Apollo to the Moon - Interview". IslamOnline. http://www.islamonline.net/servlet/Satellite?c=Article_C&cid=1169545087624&pagename=Zone-English-HealthScience%2FHSELayout. 
  3. Ruggles, C.L.N. (2005), Ancient Astronomy, pages 354-355. ABC-Clio. ISBN 1-85109-477-6.
  4. Krupp, E.C. (1988). "Light in the Temples", in C.L.N. Ruggles: Records in Stone: Papers in Memory of Alexander Thom. CUP, 473-499. ISBN 0-521-33381-4.
  5. Otto E. Neugebauer (1975), A history of ancient mathematical astronomy, Birkhäuser, ISBN 354006995X 
  6. Rufus, W. Carl, "The astronomical system of Copernicus", Popular Astronomy 31: 510–521 [512], http://adsabs.harvard.edu/full/1923PA.....31..510R, retrieved on 4 March 2010 
  7. Clement of Alexandria, Stromata, vi. 4
  8. O Neugebauer, Egyptian Planetary Texts, Transactions, American Philosophical Society, Vol. 32, Part 2, 1942, Page 237.
  9. 9.0 9.1 (Zaimeche 2002)
  10. 10.0 10.1 Dr. Emily Winterburn (National Maritime Museum) (2005). "Using an Astrolabe". Foundation for Science Technology and Civilisation. http://www.muslimheritage.com/topics/default.cfm?ArticleID=529. Retrieved on 2008-01-22. 
  11. 11.0 11.1 Toomer, G. J. (December 1964), "Review: Ibn al-Haythams Weg zur Physik by Matthias Schramm", Isis 55 (4): 463–465 [463–4], doi:10.1086/349914 
  12. (Rosen 1985, pp. 19–20 & 21)
  13. Josep Puig Montada (September 28, 2007). "Ibn Bajja". Stanford Encyclopedia of Philosophy. http://plato.stanford.edu/entries/ibn-bajja. Retrieved on 2008-07-11. 
  14. Mohamed, Mohaini (2000), Great Muslim Mathematicians, Penerbit UTM, pp. 49–50, ISBN 9835201579 
  15. Hamid-Eddine Bouali, Mourad Zghal, Zohra Ben Lakhdar (2005). "Popularisation of Optical Phenomena: Establishing the First Ibn Al-Haytham Workshop on Photography" (PDF). The Education and Training in Optics and Photonics Conference. http://spie.org/etop/ETOP2005_080.pdf. Retrieved on 2008-07-08. 
  16. S. Pines (September 1964). "The Semantic Distinction between the Terms Astronomy and Astrology according to al-Biruni", Isis 55 (3): 343-349.
  17. (Saliba 1994b, pp. 60 & 67–69)
  18. (Sabra 1998, p. 300)
  19. "Nicolaus Copernicus", Stanford Encyclopedia of Philosophy, 2004, http://setis.library.usyd.edu.au/stanford/entries/copernicus/index.html, retrieved on 22 January 2008 
  20. (Langermann 1990, pp. 25–34)
  21. (Duhem 1969, p. 28)
  22. (Rashed 2007)
  23. (Rashed 2007, pp. 20 & 53)
  24. (Rashed 2007, pp. 33–4)
  25. (Rashed 2007, pp. 20 & 32–33)
  26. (Rashed 2007, pp. 51–2)
  27. (Rashed 2007, pp. 35–6)
  28. 28.0 28.1 (Baker & Chapter 2002)
  29. (Marmura 1965)
  30. 30.0 30.1 30.2 (Saliba 1999)
  31. 31.0 31.1 "Khwarizm". Foundation for Science Technology and Civilisation. http://muslimheritage.com/topics/default.cfm?ArticleID=482. Retrieved on 2008-01-22. 
  32. 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.
  33. 33.0 33.1 33.2 (Covington 2007)
  34. (Nasr 1993, p. 134)
  35. (Saliba 1980, p. 249)
  36. (Saliba 1981, p. 219)
  37. Sabra, A. I., "The Andalusian Revolt Against Ptolemaic Astronomy: Averroes and al-Bitrûjî", in Mendelsohn, Everett, Transformation and Tradition in the Sciences: Essays in honor of I. Bernard Cohen, Cambridge University Press, pp. 233–53 
  38. 38.0 38.1 38.2 (Saliba 1994b, pp. 233–234 & 240)
  39. (Dallal 1999, p. 171)
  40. (Saliba 1979)
  41. 41.0 41.1 (Gill 2005)
  42. Y. M. Faruqi (2006). "Contributions of Islamic scholars to the scientific enterprise", International Education Journal 7 (4): 395-396.
  43. (King 2004)
  44. Richard Nelson Frye, Golden Age of Persia, p. 163.
  45. L. C. Martin (1923), Surveying and navigational instruments from the historical standpoint, 24, pp. 289–303 [289], doi:10.1088/1475-4878/24/5/302 
  46. Victor J. Katz & Annette Imhausen (2007), The mathematics of Egypt, Mesopotamia, China, India, and Islam: a sourcebook, Princeton University Press, p. 519, ISBN 0691114854 
  47. Elly Dekker (1995), "An unrecorded medieval astrolabe quadrant from c. 1300", Annals of Science 52 (1): 1-47 [6].
  48. 48.0 48.1 King, David A., "Astronomy and Islamic society", pp. 163–8 , in (Rashed & Morelon 1996, pp. 128–184)
  49. (King, Cleempoel & Moreno 2002, p. 333)
  50. 50.0 50.1 (King 1983, p. 533)
  51. 51.0 51.1 (King 2002, pp. 237–238)
  52. 52.0 52.1 King, David A. (1987), Islamic Astronomical Instruments, London: Variorum 
  53. King, David A. (1974), "An analog computer for solving problems of spherical astronomy: The Shakkaziya quadrant of Jamal al-Din al-Maridini", Archives Internationales d'Histoire des Sciences (International Archives on the History of Science) 24: 219–42 
  54. (King 1999a, pp. 168–9)
  55. "History of the sundial". National Maritime Museum. http://www.nmm.ac.uk/server/show/conWebDoc.353. Retrieved on 2008-07-02. 
  56. Jones, Lawrence (December 2005), "The Sundial And Geometry", North American Sundial Society 12 (4) 
  57. 57.0 57.1 Sabra, A. I. & Hogendijk, J. P. (2003), The Enterprise of Science in Islam: New Perspectives, MIT Press, pp. 85-118, ISBN 0262194821
  58. O. S. Marshall (1950). "Alhazen and the Telescope", Astronomical Society of the Pacific Leaflets 6, p. 4
  59. Richard Powers (University of Illinois), Best Idea; Eyes Wide OpenNew York Times, April 18, 1999.
  60. 60.0 60.1 V. J. Katz, A History of Mathematics: An Introduction, p. 291.
  61. 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.
  62. D. Campbell, Arabian Medicine and Its Influence on the Middle Ages, p. 6.
  63. Charles Burnett, ed. Adelard of Bath, Conversations with His Nephew, (Cambridge: Cambridge University Press, 1999), p. xi.
  64. M.-T. d'Alverny, "Translations and Translators," pp. 440-3
  65. G. G. Joseph, The Crest of the Peacock, p. 306
  66. Ahmad Y al-Hassan & Donald R. Hill (1986), “Islamic Technology”, Cambridge, ISBN 0-521-422396, p. 59
  67. 67.0 67.1 Topdemir, Hüseyin Gazi (1999), Takîyüddîn'in Optik Kitabi, Ministry of Culture Press, Ankara  (cf. Dr. Hüseyin Gazi Topdemir (30 June 2008). "Taqi al-Din ibn Ma‘ruf and the Science of Optics: The Nature of Light and the Mechanism of Vision". FSTC Limited. http://muslimheritage.com/topics/default.cfm?ArticleID=951. Retrieved on 2008-07-04. )
  68. Zaken, Avner Ben (2004), "The heavens of the sky and the heavens of the heart: the Ottoman cultural context for the introduction of post-Copernican astronomy", The British Journal for the History of Science (Cambridge University Press) 37: 1–28 
  69. 69.0 69.1 Salim Al-Hassani (19 June 2008). "The Astronomical Clock of Taqi Al-Din: Virtual Reconstruction". FSTC. http://muslimheritage.com/topics/default.cfm?ArticleID=947. Retrieved on 2008-07-02. 
  70. Sayili, Aydin (1991), The Observatory in Islam, pp. 289–305  (cf. Dr. Salim Ayduz (26 June 2008). "Taqi al-Din Ibn Ma’ruf: A Bio-Bibliographical Essay". http://muslimheritage.com/topics/default.cfm?ArticleID=949. Retrieved on 2008-07-04. )

ReferencesEdit

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Further readingEdit

  • Marshall Clagett, (2004), Ancient Egyptian Science: A Source Book. Volume Two: Calendars, Clocks, and Astronomy. American Philosophical Society. ISBN 0-871-69214-7

12px This article incorporates text from a publication now in the public domainChisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press. 

External linksEdit


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