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The Great Contribution of Islamic Astronomers

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Bianca
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« Reply #15 on: August 27, 2007, 06:02:28 pm »









Ulugh Beg, founder of
a large Islamic observatory,
honoured on this Soviet stamp.
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« Reply #16 on: August 27, 2007, 06:11:15 pm »







                                                   I N S T R U M E N T S





See also: Inventions in the Muslim world



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. Their contributions to astronomical instrumentation are abundant.


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« Reply #17 on: August 27, 2007, 06:17:28 pm »



                                                 A S T R O L A B E S






Brass astrolabe




FOR HISTORY OF ASTROLABE SEE:

http://atlantisonline.smfforfree2.com/index.php/topic,2764.0.html



Brass astrolabes were developed in much of the Islamic world, chiefly 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 (Richard Nelson Frye: Golden Age of Persia. p163). He only improved it though, the Greeks had already invented astrolabes to chart the stars. The Arabs then took it during the Abbasid Dynasty and perfected it to be used to find the beginning of Ramadan, the hours of prayer, and the direction of Mecca.






Saphaea



SEE:

http://atlantisonline.smfforfree2.com/index.php/topic,2764.0.html

The instruments were used to read the rise of the time of rise of the Sun and fixed stars. Arzachel (Al-Zarqali) of Al-Andalus constructed one such instrument in which, unlike its predecessors, did not depend on the latitude of the observer, and could be used anywhere. This instrument became known in Europe as the Saphaea.




Mechanical astrolabe

Mechanical astrolabes were developed in the Muslim world, and were perfected by Ibn Samh. These can be considered as an ancestor of the mechanical clocks developed by later Muslim engineers.[44]




Orthographical astrolabe

Abu Rayhan al-Biruni invented and wrote the earliest treatise on the orthographical astrolabe in the 1000s.[17]



 Linear astrolabe

A famous work by Sharaf al-Dīn al-Tūsī is one in which he describes the linear astrolabe, sometimes called the "staff of al-Tusi", which he invented.
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« Reply #18 on: August 27, 2007, 06:25:00 pm »

Armillary spheres and spherical astrolabes






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. In this context there is also an Islamic development, the spherical astrolabe, of which only one complete instrument, from the 14th century, has survived.

Early man, looking at the heavens, believed the stars were fixed to the inside surface of a rotating sphere. From a modern perspective it's pretty strange to assume that our world is the center of the Universe. We now know that we live on the fringe of a nearly infinite and ever expanding universe. Armillary spheres have the earth positioned inside a mesh of bronze hoops, symbolizing the course of the planets as known at the time.

The course of the Sun is shown by a wide band called the ecliptic circle. Armillary or astronomical spheres go back to B.C. Greece.

 Muslim astronomers were the first to develop this unique instrument.

� Closely related to astrolabes and armillary spheres, astronomical armillaries are a form of celestial globes and are based on a model of an outer sphere of stars and celestial bodies which circled the Earth. � The first models were built in an attempt to represent the complicated movements that were occurring in the heavens. �

Over time, many features were added to the original models which included the equator, poles and additional rings. � Astronomers were able to use the instrument to predict star and constellation movements, determine the precise time the sun would rise and set, and find the position of the Earth by using the night sky. �

This decorative reproduction of a astronomical armillary includes the names of the 12 astrological signs engraved into the globe in Arabic letters. � The concentric rings, which rotate 360 degrees and are held together on a center axis, are intricately engraved with the signs of the Zodiac and are printed with the Zodiac�s Arabic name on the outer rim. � The armillary is made from solid brass, and hangs from two suspension loops. �   

This Astronomical Armillary�s largest ring measures 13.5 inches (34.3 cm) in diameter, 17 inches (43.2 cm) tall, and the center hollow globe sphere is 4 inches in diameter (10.2 cm). � The Astronomical Armillary is very heavy weighing 6 pounds, 13 ounces (3.1 kg) and is suitable for hanging from a shelf or a ceiling. 

http://www.stanleylondon.com/astroarmillary.htm

 



Astronomical clock






The Muslims constructed a variety of highly accurate astronomical clocks for use in their observatories.






Celestial globes





ISLAMIC CELESTIAL GLOBE


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.
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« Reply #19 on: August 27, 2007, 06:27:41 pm »





Equatorium

The Equatorium is an Islamic invention from Andalusia. The earliest known was probably made around 1015 CE. It is a mechanical device for finding the positions of the Moon, Sun, and planets, without calculation using a geometrical model to represent the celestial body's mean and anomalistic position.







Planisphere

Abu Rayhan al-Biruni invented and wrote the earliest treatise on the planisphere in the 1000s.[17]





Quadrants

Several forms of quadrants were invented by Muslims. Among them was the sine quadrant used for astronomical calculations and various forms of the horary quadrant, used to determine time (especially the times of prayer) by observations of the Sun or stars. A center of the development of quadrants was ninth-century Baghdad.






Sextant

The first sextant was constructed in Ray, Iran, by Abu-Mahmud al-Khujandi in 994. It was a very large sextant that achieved a high level of accuracy for astronomical measurements, which he described his in his treatise, On the obliquity of the ecliptic and the latitudes of the cities.





Sundials

Muslims made several important improvements to the theory and construction of sundials, which they inherited from their Indian and Hellenistic predecessors. Khwarizmi made tables for these instruments which considerably shortened the time needed to make specific calculations.



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 Umayyid Mosque in Damascus, Ibn al-Shatir.
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« Reply #20 on: August 27, 2007, 06:30:24 pm »










"Where are we?" Normally, this is a routine question answered several times a day while saling along safely in mid ocean. But the question has a different urgency when the ship is approaching a rocky coast and the life of the ship and its crew depends on a fast and accurate fix of position.  It's the Navigator's job to provide the answer.
So what do navigators need to find their position on the earth's surface by observing the stars? 
They need an Almanac prepared by the astronomers to forecast precisely where the heavenly bodies, the sun, moon planets and selected navigational stars, are going to be, hour by hour, years into the future, relative to the observatory that prepared the almanac, Greenwich, England in modern times.
They need a chronometer or some other means of telling the time back at the observatory that was the reference point for the data in the almanac,
It is the cartographer's job to provide accurate charts so that navigators can establish their position in latitude and longitude or in reference to landmasses or the hazards of rocks and shoals. 
The navigators need a quick and easy mathematical method for reducing the data from their celestial observations to a position on the chart
Finally, navigators need an angle-measuring instrument, a sextant, to measure the angle of the celestial body above a horizontal line of reference. 
How do navigators use the stars, including our sun, the moon, and planets to find their way?  Well, for at least two millennia, navigators have known how to determine their latitude-their position north or south of the equator. At the North Pole, which is 90 degrees latitude, Polaris (the North Star) is directly overhead at an altitude of 90 degrees. At the equator, which is zero degrees latitude, Polaris is on the horizon with zero degrees altitude.  Between the equator and the North Pole, the angle of Polaris above the horizon is a direct measure of terrestrial latitude.  If we were to go outside tonight and look in the northern sky, we would find Polaris at  the latitude where we are at that moment. 
In ancient times, the navigator who was planning to sail out of sight of land would simply measure the altitude of Polaris as he left homeport, in today's terms measuring the latitude of home port. To return after a long voyage, he needed only to sail north or south, as appropriate, to bring Polaris to the altitude of home port, then turn left or right as as appropriate and “sail down the latitude,” keeping Polaris at a constant angle.
The Arabs knew all about this technique. In early days, they used one or two fingers width, a thumb and little finger on an outstretched arm or an arrow held at arms length to sight the horizon at the lower end and Polaris at the upper end.           
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« Reply #21 on: August 31, 2007, 07:32:01 pm »






An Arabic Kamal     

 
In later years, they used a simple device called a kamal to make the observation.  The kamal shown here actually is a modern piece that I made, but it's very much like the ones used a thousand years ago, and probably much earlier.  Notice the knots in the cord attached to the carved mahogany transom. Before leaving homeport, the navigator would tie a knot in the cord so that, by holding it in his teeth, he could sight Polaris along the top of the transom and the horizon along the bottom.
To return to homeport, he would sail north or south as needed to bring Polaris to the altitude he'd observed when he left home, then sail down the latitude. Over time, Arab navigators started tying knots in the string at intervals of one issabah. The word issabah is Arabic for finger, and it denotes one degree 36 minutes, which was considered to be the width of a finger. They even developed a journal of different ports that recorded which knot on the kamal corresponded to the altitude of Polaris for each port they frequently visited.
Throughout antiquity, the Greeks and Arabs steadily advanced the science of astronomy and the art of astrology.  About a thousand years ago, in the 10th century, Arabs introduced Europe to two important astronomical instruments-the quadrant and the astrolabe.


http://www.clipperlight.com/infosextant.html
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« Reply #22 on: August 31, 2007, 08:19:41 pm »

                    







                               
In Islamic Spain, the high civilization of the Umayyad caliphs in Damascus was first continued, then exceeded, as both eastern and homegrown scholars and artists found welcoming and openhanded patrons in al-Andalus. One example is the ninth-century scholar ‘Abbas ibn Firnas, who experimented with flight some 600 years before Leonardo da Vinci and constructed a planetarium in which the planets actually revolved.
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« Reply #23 on: August 31, 2007, 08:27:01 pm »








The Medieval Christians of Spain had a legend that Roderick, the last king of the Visigoths, was responsible for unleashing the Arab invasion of the Iberian Peninsula because, in defiance of his plighted word, he unlocked the gates of an enchanted palace he had sworn not to tamper with. As far as the West was concerned, the Arab invasion did unlock an enchanted palace. Following the collapse of the Roman Empire, Vandals, Huns and Visigoths had pillaged and burned their way through the Iberian Peninsula, establishing ephemeral kingdoms which lasted only as long as loot poured in, and were then destroyed in their turn. Then, without warning, in the year 711, came the Arabs—to settle, fall in love with the land and create the first civilization Europe had known since the Roman legions gave up the unequal fight against the barbarian hordes.

Spain first prospered under the rule of the Umayyads, who established a dynasty there after they had lost the caliphate in the East to the Abbasids. At first, the culture of the Umayyad court at Córdoba was wholly derivative. Fashions, both in literature and dress, were imitiative of those current in the Abbasids’ newly founded capital of Baghdad. Scholars from the more sophisticated lands to the east were always assured of a warm reception at the court of Córdoba, where their colleagues would listen avidly for news of what was being discussed in the capital, what people were wearing, what songs were being sung, and—above all—what books were being read.

Islamic culture was pre-eminently a culture of the book. The introduction of paper from China in 751 gave an impetus to learning and an excitement about ideas which the world had never before known. Books became more available than they had been even in Rome, and incomparably cheaper than they were in the Latin West, where they continued to be written on expensive parchment. In the 12th century, a man sold 120 acres of land in order to buy a single Book of Hours. In the ninth century, the library of the monastery of St. Gall was the largest in Europe, boasting 36 volumes. At the same time, that of Córdoba contained 500,000. The cultural lag between East and West in the Middle Ages can be attributed partly to the fact that the Arabs had paper, while the Latin West did not.
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« Reply #24 on: August 31, 2007, 08:28:47 pm »








It took much more than paper to create an intellectual and scientific culture like that of Islamic Spain, of course. Islam, with its tolerance and encouragement of both secular and religious learning, created the necessary climate for the exchange of ideas. The court of Córdoba, like that of Baghdad, was open to Muslims, Jews and Christians alike, and one prominent bishop complained that young Christian men were devoting themselves to the study of Arabic, rather than Latin—a reflection of the fact that Arabic, in a surprisingly short time, had become the international language of science, as English has today.

Islamic culture in Spain began to flourish in earnest during the reign of ‘Abd al-Rahman II of Córdoba, as Arabic spread increasingly among his non-Muslim subjects, especially in the cities, leading to a great flowering of intellectual activity of all kinds.

In a courtly society, the tastes and predilections of the ruler set the tone for society at large, and ‘Abd al-Rahman II, passionately interested in both the religious and the secular sciences, was determined to show the world that his court was in no way inferior to the court of the caliphs at Baghdad. To this end, therefore, he actively recruited scholars by offering handsome inducements to overcome their initial reluctance to live in what many in the lands of the East considered the provinces. As a result, many scholars, poets, philosophers, historians and musicians migrated to al-Andalus, and established the basis of the intellectual tradition and educational system which made Spain so outstanding for the next 400 years.

Another result was that an infrastructure of public and private libraries, mosques, hospitals and research institutions rapidly grew up and famous scholars in the East, hearing of these amenities, flocked to the West. They in turn attracted students of their own; in the Islamic world it was not at all unusual for a student to travel thousands of miles to study at the feet of a famous professor.
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« Reply #25 on: August 31, 2007, 08:30:18 pm »








Another result was that an infrastructure of public and private libraries, mosques, hospitals and research institutions rapidly grew up and famous scholars in the East, hearing of these amenities, flocked to the West. They in turn attracted students of their own; in the Islamic world it was not at all unusual for a student to travel thousands of miles to study at the feet of a famous professor.

One of the earliest of these scholars was ‘Abbas ibn Firnas, who died in the year 888 and who, had he lived in the Florence of the Medici, would have been a “Renaissance man.” He came to Córdoba to teach music, then a branch of mathematical theory, but—not a man to limit himself to a single field of study—soon became interested in the mechanics of flight. He constructed a pair of wings, made out of feathers in a wooden frame, and attempted to fly—anticipating Leonardo da Vinci by some 600 years.

Luckily, ‘Abbas survived, and, undiscouraged, turned his mind to the construction of a planetarium in which the planets actually revolved—it would be extremely interesting to know the details of the gearing mechanism. It also simulated such celestial phenomena as thunder and lightning and was, of course, a wild success. Next ‘Abbas turned to the mathematical problems involved in the regularity of the facets of certain crystals and evolved a formula for manufacturing artificial crystals.
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« Reply #26 on: August 31, 2007, 08:34:41 pm »

                     







t must be remembered that a knowledge of the achievements of men like ‘Abbas has come to us purely by chance. It has been estimated that today there are 250,000 Arabic manuscripts in western and eastern libraries, including private collections. Yet in the 10th century, private libraries existed which contained as many as 500,000 books. Literally millions of books must have perished, and with them the achievements of a great many scholars and scientists whose books, had they survived, might have changed the course of history. As it is, even now, only a tiny proportion of existing Arabic scientific texts has been studied, and it will take years to form a more exact idea of the contributions of Muslim scientists to the history of ideas.

One of the fields most assiduously cultivated in Spain was natural science. Although Andalusian scholars did not make contributions as fundamental as those made by their colleagues in the East, those that they did make had more effect on the later development of science and technology, for it was through Spain and the scholars of al-Andalus that these ideas reached the West.

No school of translators comparable to the House of Wisdom of al-Ma’mun existed in Spain, and Andalusian scholars seem not to have interested themselves in the natural sciences until the translations of the House of Wisdom reached them.
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« Reply #27 on: August 31, 2007, 08:40:32 pm »








Interest in mathematics, astronomy, and medicine was always lively, however, because of their obvious utility—mathematics for commercial purposes, computation of the rather complicated Islamic laws of inheritance, and as a basis for measuring distances. Astronomy was useful for determining the times of prayer and adjusting the calendar, and the study of medicine needed no apology. The introduction of the new Aristotelian ideas, however, even in Arab dress, aroused a certain amount of suspicion in the conservative West, and it was some time before public opinion would accept that Aristotelian logic did not conflict with the revelation of Islam.

Part of the suspicion with which certain of the ideas emanating from the scholars of the Abbasid court were viewed was due to an inadequate distinction between sciences and pseudo-sciences. This was a distinction which the Muslims made at a much earlier date than western scholars, who, even during the Renaissance, tended to confound astronomy with astrology, chemistry with alchemy. Ibn Hazm, a leading Andalusian scholar of the 11th century and staunchly conservative, was very outspoken on this point. People who advocated the efficacy of talismans, magic, alchemy, and astrology he calls shameless liars. This rational approach did much to make Islam preeminent in the natural sciences.

The study of mathematics and astronomy went hand in hand. Al-Khwarizmi’s famous book entitled The Calculation of Integration and Equation reached al-Andalus at an early date, and became the foundation of much later speculation. In it, Al-Khwarizmi dealt with equations, algebraic multiplication and division, measurement of surfaces and other questions. Al-Khwarizmi was the first to introduce the use of what he called “Indian” and we call “Arabic” numerals.

The exact method of transmission of these numerals—and the place-value idea which they embodied—is not known, but the symbols used to represent the numbers had slightly different forms in eastern and western Islam, and the forms of our numerals are derived from those used in al-Andalus. The work of al-Khwarizmi, which now only survives in a 12th-century Latin translation made in Spain, together with a translation of Euclid’s Elements, became the two foundations of subsequent mathematical developments in al-Andalus.
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« Reply #28 on: August 31, 2007, 08:43:01 pm »






The first original mathematician and astronomer of al-Andalus was the 10th century’s Maslama al-Majriti. He had been preceded by competent scientists—men like Ibn Abi ‘Ubaida of Valencia, who in the ninth century was a leading astronomer, and the emigré from Baghdad, Ibn Taimiyyah, who was both a well-known physician and an astronomer—but al-Majriti was in a class by himself. He wrote a number of works on mathematics and astronomy, studied and elaborated the Arabic translation of Ptolemy’s Almagest and enlarged and corrected the astronomical tables of al-Khwarizmi himself. He compiled conversion tables, in which the dates of the Persian calendar were related to hijri dates, so that for the first time the events of Persia’s past could be dated with precision.
                   
Al-Zarqali, known to the Latin West as Arzachel, was another leading mathematician and astronomer who flourished in Córdoba in the 11th century. He combined theoretical knowledge with technical skills, and excelled at the construction of precision instruments for astronomical use. He built a waterclock capable of determining the hours of the day and night and indicating the days of the lunar month. He contributed to the compilation of the famous Toledan Tables, a highly accurate compilation of astronomical data. His Book of Tables, written in the form of an almanac (almanac is an Arabic word meaning “climate,” originally indicating the stations of the moon) contains tables which allow one to find on what day the Coptic, Roman, lunar and Persian months begin; others give the position of the various planets at any given time; still others allow prediction of solar and lunar eclipses. He also compiled valuable tables of latitude and longitude; many of his works were translated, both into Spanish and into Latin.
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« Reply #29 on: August 31, 2007, 08:58:51 pm »








Still another luminary was al-Bitruji (the Latin scholars of the Middle Ages called him Alpetragius), who developed a new theory of stellar movement and wrote the Book of Form in which it is detailed.

The influence of these astronom- ical works was immense. Today, for example, the constellations still bear the names given them by Muslim astronomers—Acrab (from ‘aqrab, “scorpion”), Altair (from al-ta’ir, “the flyer”), Deneb (from dhanb, “tail”), Pherkard (from farqad, “calf”)—and words such as zenith, nadir and azimuth, all still in use today, recall the works of the Muslim scholars of al-Andalus.
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