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The Great Contribution of Islamic Astronomers

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Bianca
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« Reply #45 on: October 12, 2008, 10:48:10 pm »












                                           I S L A M I C   A S T R O L O G Y






Islamic astrology, in Arabic ilm al-nujum or ilm al-falak, is the study of the heavens by early Muslims.

In early Arabic sources, ilm al-nujum was used to refer to both astronomy and astrology.




In medieval sources, however, a clear distinction was made between 'ilm al-nujum'
(science of the stars)

or ilm al-falak (science of the celestial orbs), referring to astrology, and 'ilm al-hay'ah'
(science of the figure of the heavens), referring to astronomy.




Both fields were rooted in Greek, Persian, and Indian traditions.

Despite consistent critiques of astrology by scientists and religious scholars, astrological prognostications required a fair amount of exact scientific knowledge and thus gave partial
incentive for the study and development of astronomy.
The earliest semantic distinction between astronomy and astrology was given by the Persian astronomer and astrologer Abu Rayhan al-Biruni circa 1000.
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« Reply #46 on: October 13, 2008, 09:17:27 am »










Opinions of contemporary scholars



According to jurists, the study of astronomy (ilm al-hay'ah) is lawful, as it is useful in predicting the beginning of months and seasons, determining the direction of salat (prayer), and navigation. They agree that this branch of science be used in determining the beginning and end of the month of Ramadan. As for astrology, this is considered by many Islamic scholars as haram (unlawful), as knowledge of the Unseen is known only by Allah. Dr. Husam al-Din Ibn Musa `Afana, a Professor of
the Principles of Fiqh at Al-Quds University, Palestine, states the following:



"First of all, it is worth noting that the Arabs knew astronomy a long time ago. They would predict time through observing the movements of stars. According to the scholars of Shar`iah, there are two terms confused in many people's minds when it comes to dealing with the question in hand. These terms are astronomy and astrology. Astronomy is the science that deals with studying the movements of the celestial bodies and reducing observations to mathematical order. That science is useful in determining time, seasons, the direction of Prayer, etc. Astrology, on the other hand, is concerned with studying the positions and aspects of celestial bodies in the belief that they have an influence on the course of natural earthly occurrences and human affairs. Astrologists believe that the movements of stars have an influence on people's lives. Both Muslim astronomers and [religious] scholars refuse the prophecies of astrologists."



Some scholars believe that astrology is a prohibited field of study. Imam Ibn Taymiyah said: “Astrology that is concerned with studying the positions and aspects of celestial bodies in the belief that they have an influence on the course of natural earthly occurrences and human affairs is prohibited by the Quran, the Sunnah, and the unanimous agreement of the Muslim scholars. Furthermore, astrology was considered forbidden by all Messengers of Almighty Allah.”

The Saudi scholar, Muhammad ibn al Uthaymeen, said: “Astrology is a kind of sorcery and fortune-telling. It is forbidden because it is based on illusions, not on concrete facts. There is no relation between the movements of celestial bodies and what takes place on the Earth.”
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« Reply #47 on: October 13, 2008, 09:19:14 am »










Refutations of astrology



The first semantic distinction between astrology and astronomy was given by the Persian Muslim astronomer Abu Rayhan al-Biruni in the 11th century,[4] and he later refuted astrology in another treatise. The study of astrology was also refuted by other medieval Muslim astronomers such as Al-Farabi (Alpharabius), Ibn al-Haytham (Alhazen), 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.

Ibn Qayyim Al-Jawziyya (1292-1350), in his Miftah Dar al-SaCadah, used empirical arguments in astronomy in order to refute the practice of astrology and divination.  He recognized that the stars
are much larger than the planets, and thus argued:



"And if you astrologers answer that it is precisely because of this distance and smallness that their influences are negligible, then why is it that you claim a great influence for the smallest heavenly body, Mercury? Why is it that you have given an influence to al-Ra's and al-Dhanab, which are two imaginary points [ascending and descending nodes]?"



Al-Jawziyya also recognized the Milky Way galaxy as "a myriad of tiny stars packed together in the sphere of the fixed stars" and thus argued that "it is certainly impossible to have knowledge of their influences."
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« Reply #48 on: October 13, 2008, 09:22:12 am »










Quranic verses and Ahadith relating to astrology



Before the advent of Islam, people believed that the sun and moon might eclipse when a great figure died. During Muhammad's lifetime, it happened that the sun eclipsed on the same day when Muhammad’s son Ibrahim died. The people then thought that it had eclipsed because of Muhammad’s son’s death. On knowing this, Muhammad led them in the Eclipse Prayer and then delivered a speech saying: “The sun and moon are but signs of Allah; they do not eclipse because so-and-so died or was born.”

This hadith indicates that Muhammad denied all relation between the movements of the heavenly bodies and events on the Earth. Ibn `Abbas reported that Muhammad said: “He who has acquired some knowledge of astrology has acquired some knowledge of sorcery; the more he acquires of the former the more he acquires of the latter.”

Commenting on this hadith, the Yemeni scholar Muhammad ash-Shawkani (d.1834), said that the Islamic prophet Muhammad compared between astrology and sorcery because sorcery was known to be forbidden; and so, he who would get some knowledge of astrology would do something forbidden and would be sinful.

It was also reported by Ibn Abbas that Muhammad said: “He who uses astronomy for something other than what Almighty Allah has made lawful would be practicing sorcery. Astrologers predict knowledge
of the future, and he who does so is a sorcerer, and sorcerers are disbelievers.”

Also, Ibn Mihjan reported that Muhammad said: “I fear on account of my nation three things after my death: (I fear that) their Imams (leaders) would oppress them, (that) they would believe in astrology, and (that) they would disbelieve predestination.”

Abu Hurayrah also reported that Muhammad said: “He who goes to a fortune-teller to ask him about something, his Prayer will not be accepted for forty days.”

Abu Hurayrah also reported that Muhammad said: “He who goes to a soothsayer or a fortuneteller and believes what he says exhibits disbelief in what has been sent down to Prophet Muhammad (from Allah).”

Contemplating the last two ahadith reported by Abu Hurayrah, it is to be noted that mere going to fortune-tellers is a sin that incurs upon a Muslim who commits it that his prayer is not accepted for forty days, and that believing what fortunetellers say renders a Muslim a disbeliever in what has been sent down to Muhammad. This is because Allah says in the Quran: “Say (O Muhammad): None in the heavens and the earth knoweth the Unseen save Allah; and they know not when they will be raised (again).”


Allah also says:

“(He is) the knower of the Unseen, and He revealeth unto none His secret, save unto every messenger whom he hath chosen, and then He maketh a guard to go before him and a guard behind him That He may know that they have indeed conveyed the messages of their Lord. He surroundeth all their doings, and He keepeth count of all things.”
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« Reply #49 on: October 13, 2008, 09:24:58 am »








               Prominent Arab, Muslim, Persian, and/or Middle Eastern or North African astrologers






This is an incomplete list, which may never be able to satisfy certain standards for completeness.

Revisions and additions are welcome.



Abraham ibn Ezra

Abraham Zacuto
 
Al-Battani

Al-Biruni

Albubather
 
Alchabitius

Al-fadl ibn Naubakht

'Ali ibn Ridwan

Al-Kindī

Arzachel

Berossus

Biblical Magi (the "Three Wise Men")

Haly Abenragel

Hypatia of Alexandria

Ibn Arabi

Ibn Yunus

Ibrahim al-Fazari

Ja'far ibn Muhammad Abu Ma'shar al-Balkhi

Mashallah

Muhammad al-Fazari

Muhammad ibn Musa al-Khwarizmi

Naubakht

Porphyry

Sharafeddin Tusi

Sudines

Taqi al-Din



http://en.wikipedia.org/wiki/Islamic_astrology



http://en.wikipedia.org/wiki/Islamic_astrology
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« Reply #50 on: October 13, 2008, 09:29:02 am »










                                                    Astronomy in medieval Islam






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. In turn, Islamic astronomy later had a significant influence on Indian and European astronomy (see Latin translations of the 12th century) as well as Chinese astronomy.

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 catalogued. Even so, a reasonably accurate picture of Islamic activity in the field of astronomy can be reconstructed.
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« Reply #51 on: October 13, 2008, 09:31:43 am »










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.

In the 7th century, both Christians and Jews observed holy days, such as Easter and Passover, whose timing was determined by the phases of the moon. Both communities had confronted the fact that the approximately 29.5-day lunar months are not commensurable with the 365-day solar year. To solve the problem, Christians and Jews had adopted a scheme based on a discovery made in circa 430 BC by the Athenian astronomer Meton. In the 19-year Metonic cycle, there were 12 years of 12 lunar months and seven years of 13 lunar months. The periodic insertion of a 13th month kept calendar dates in step with the seasons.

On the other hand, astronomers used Ptolemy's way to calculate the place of the moon and stars.

The method Ptolemy used to solve spherical triangles was a clumsy one devised late in the first century by Menelaus of Alexandria.

It involved setting up two intersecting right triangles; by applying Menelaus' theorem it was possible
to solve one of the six sides, but only if the other five sides were known. To tell the time from the sun's altitude, for instance, repeated applications of Menelaus' theorem were required. For medieval Islamic astronomers, there was an obvious challenge to find a simpler trigonometric method.
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« Reply #52 on: October 13, 2008, 09:33:36 am »










Islam advised Muslims to find ways of using the stars. The Qur'an says: "And it is He who ordained the stars for you that you may be guided thereby in the darkness of the land and the sea."

On the basis of this advice Muslim began to find better observational and navigational instruments, thus most navigational stars today have Arabic names.

Other influences of the Qur'an on Islamic astronomy included its "insistence that the Universe is ruled by a single set of laws" which was "rooted in the Islamic concept of tawhîd, the unity of God", as well its "greater respect for empirical data than was common in the preceding Greek civilization" which inspired Muslims to place a greater emphasis on empirical observation,[8] 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:

“The general empirical attitude of the Qur'an which engendered in its followers a feeling of reverence for the actual, and ultimately made them the founders of modern science. It was a great point to awaken the empirical spirit in an age that renounced the visible as of no value in men's search after God.”

There are also several 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.Qur'an 51:47

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."
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« Reply #53 on: October 13, 2008, 09:36:12 am »










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 is the straight usage."



Therefore Muslims could not follow the Christian or Hebrew calendars and they thus had to develop a new one.

The other issue is moon sighting. Islamic months do not begin at the astronomical new moon, defined as the time when the moon has the same celestial longitude as the sun and is therefore invisible; instead they begin when the thin crescent moon is first sighted in the western evening sky.

The Qur'an says:


"They ask you about the waxing and waning phases of the crescent moons, say they are to mark

fixed times for mankind and Hajj."


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.
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« Reply #54 on: October 13, 2008, 09:37:59 am »









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).
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« Reply #55 on: October 13, 2008, 09:39:57 am »









History



Pre-Islamic Arabian knowledge of stars was empirical; their knowledge was what they observed regarding the rising and setting of stars. The rise of Islam is claimed to have provoked increased Arab thought in this field.[20] 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:[20]

Assimilation and syncretization of earlier Hellenistic, Indian and Sassanid astronomy (700—825 AD)
Vigorous investigation, and acceptance and modification to the Ptolemaic system (825—1025 AD)
Flourishing of a distinctive Islamic system of astronomy (1025—1450 AD)
Stagnation, where few significant contributions were made (1450—1900 AD)




610-700


From the beginning, Muslim community in Medina sight new moon to determine the lunar months especially Ramadan and holy days.

In approximately 638 A.D, Caliph Umar introduced a new lunar calendar which is known as lunar calendar was made on the basis of Islamic view point. This calendar has twelve lunar months, the beginnings of which are determined by the sighting of the crescent moon. This calendar is about 11 days shorter than the solar year. This calendar is still in use for religious purposes among Muslims.




 700-825


This period was most notably the period of assimilation and syncretization of earlier Hellenistic, Indian and Sassanid astronomy occurred during the eighth and early ninth centuries.



http://en.wikipedia.org/wiki/Islamic_astronomy
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« Reply #56 on: October 13, 2008, 09:42:14 am »



A page from Ptolemy's Almagest









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.
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« Reply #57 on: October 13, 2008, 09:48:05 am »









Ancient influences and translation movement


During this period, a number of Sanskrit and Middle Persian texts were first translated into Arabic.

The most notable of the texts was Zij al-Sindhind, 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.[20] Another Indian influence was an approximate formula used for timekeeping by Muslim astronomers.[23]

 
Islamic interest in astronomy ran parallel to the interest in mathematics. Especially noteworthy in this regard was the Almagest (c. 150) of the astronomer Ptolemy (c. 100-178).

The Almagest was a landmark work in its field, assembling, as Euclid's 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) 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.
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« Reply #58 on: October 13, 2008, 09:49:29 am »



Al-Khwarizmi,

the father of algebra and algorithms,
wrote the 'Zij al-Sindh',
the first original Zij in Islamic astronomy.










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.
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« Reply #59 on: October 13, 2008, 10:05:10 am »



Azophi's 'Book of Fixed Stars', which described more than a thousand stars in detail and gave the
first descriptions on the Andromeda Galaxy and Large Magellanic Cloud.

The constellation pictured here is Sagittarius.
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