Islamic cosmology

Islamic cosmology

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Islamic cosmology refers to cosmology
Cosmology
Cosmology is the discipline that deals with the nature of the Universe as a whole. Cosmologists seek to understand the origin, evolution, structure, and ultimate fate of the Universe at large, as well as the natural laws that keep it in order...

 in Islamic societies
Muslim world
The term Muslim world has several meanings. In a religious sense, it refers to those who adhere to the teachings of Islam, referred to as Muslims. In a cultural sense, it refers to Islamic civilization, inclusive of non-Muslims living in that civilization...

. It is mainly derived from the Qur'an
Qur'an
The Quran , also transliterated Qur'an, Koran, Alcoran, Qur’ān, Coran, Kuran, and al-Qur’ān, is the central religious text of Islam, which Muslims consider the verbatim word of God . It is regarded widely as the finest piece of literature in the Arabic language...

, Hadith
Hadith
The term Hadīth is used to denote a saying or an act or tacit approval or criticism ascribed either validly or invalidly to the Islamic prophet Muhammad....

, Sunnah
Sunnah
The word literally means a clear, well trodden, busy and plain surfaced road. In the discussion of the sources of religion, Sunnah denotes the practice of Prophet Muhammad that he taught and practically instituted as a teacher of the sharī‘ah and the best exemplar...

, and current Islam
Islam
Islam . The most common are and .   : Arabic pronunciation varies regionally. The first vowel ranges from ~~. The second vowel ranges from ~~~...

ic as well as other pre-Islamic sources. The Qur'an itself mentions seven heavens and a vast universe
Universe
The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

 sustained by Allah
Allah
Allah is a word for God used in the context of Islam. In Arabic, the word means simply "God". It is used primarily by Muslims and Bahá'ís, and often, albeit not exclusively, used by Arabic-speaking Eastern Catholic Christians, Maltese Roman Catholics, Eastern Orthodox Christians, Mizrahi Jews and...

.

Duality


Islamic thought categorizes the entire cosmos into two domains: the Unseen Universe (Arabic عالم الغيب , Aalam-ul-Ghaib), which is imperceptible to mankind in general, has properties unknown to us, and includes Allah(metaphorically), angels, Paradise
Paradise
Paradise is a place in which existence is positive, harmonious and timeless. It is conceptually a counter-image of the miseries of human civilization, and in paradise there is only peace, prosperity, and happiness. Paradise is a place of contentment, but it is not necessarily a land of luxury and...

, Hell
Hell
In many religious traditions, a hell is a place of suffering and punishment in the afterlife. Religions with a linear divine history often depict hells as endless. Religions with a cyclic history often depict a hell as an intermediary period between incarnations...

, seven heavens, and Al-Arsh (the Divine Throne
Throne of God
The Throne of God is the reigning centre of the chief deity of the Abrahamic faiths, Judaism, Christianity and Islam. The throne is said by various holy books to reside above the Seventh Heaven called Araboth in Judaism.-Judaism:...

)http://qurancomplex.org/Quran/Targama/Targama.asp?L=eng&Page=2; and the Observable Universe (Arabic عالم الشهود , Alam-ul-Shahood), perceptible through the five senses (possibly enhanced by means of instruments). The Qur'an says: "Allah is He, Who is the only God, the knower of the Unseen and the Observed."

Teleology


In the light of a detailed description of the creation of the Universe drawn from the Qur'an and Sunnah, the purpose of existence is for God to become known, to be discovered by human beings. Before the creation, Allah was known only to himself, because nothing existed but he. It was part of his grand design that through created beings the Attributes of Allah were to be fulfilled.

Allah may be known in two ways: through revelation and by means of reasoning. In the former case, he has conveyed his presence to humankind by sending messengers
Prophets of Islam
Muslims identify the Prophets of Islam as those humans chosen by God and given revelation to deliver to mankind. Muslims believe that every prophet was given a belief to worship God and their respective followers believed it as well...

. Individuals also may become aware of Allah's existence through personal revelations, much as a schoolchild learns from teachers and books. Reasoning may lead to awareness of God's existence through formal logic, rational arguments, or deductions from the results of scientific or historical research, according to the individual's interests, education, and aptitudes. Those who choose to study the Qur'an and Hadith may obtain further understanding of Allah, his rights, and his judgement
Islamic eschatology
Islamic eschatology is concerned with the al-Qiyāmah . Like the other Abrahamic religions, Islam teaches the bodily resurrection of the dead, the fulfillment of a divine plan for creation, and the judgement of the soul; the righteous are rewarded with the pleasures of Jannah while the unrighteous...

 of the beings in both the unseen and observable universes.

Sufi cosmology


Sufi cosmology is a general term for cosmological
Cosmology
Cosmology is the discipline that deals with the nature of the Universe as a whole. Cosmologists seek to understand the origin, evolution, structure, and ultimate fate of the Universe at large, as well as the natural laws that keep it in order...

 doctrines associated with the mysticism of Sufism
Sufism
Sufism or ' is defined by its adherents as the inner, mystical dimension of Islam. A practitioner of this tradition is generally known as a '...

. These may differ from place to place, order to order and time to time, but overall show the influence of several different cosmographies
Cosmography
Cosmography is the science that maps the general features of the universe, describing both heaven and Earth...

:
  • The Quran's testament concerning God and immaterial beings, the soul and the afterlife, the beginning and end of things, the seven heavens etc.
  • The Neoplatonic views cherished by Islamic philosophers
    Islamic philosophy
    Islamic philosophy is a branch of Islamic studies. It is the continuous search for Hekma in the light of Islamic view of life, universe, ethics, society, and so on...

     like Avicenna
    Avicenna
    Abū ʿAlī al-Ḥusayn ibn ʿAbd Allāh ibn Sīnā , commonly known as Ibn Sīnā or by his Latinized name Avicenna, was a Persian polymath, who wrote almost 450 treatises on a wide range of subjects, of which around 240 have survived...

     and Ibn Arabi
    Ibn Arabi
    Ibn ʿArabī was an Andalusian Moorish Sufi mystic and philosopher. His full name was Abū 'Abdillāh Muḥammad ibn 'Alī ibn Muḥammad ibn `Arabī .-Biography:...

    .
  • The Hermetic
    Hermeticism
    Hermeticism or the Western Hermetic Tradition is a set of philosophical and religious beliefs based primarily upon the pseudepigraphical writings attributed to Hermes Trismegistus...

    -Ptolemaic spherical geocentric world.
  • The Ishraqi visionary universe as expounded by Suhrawardi Maqtul.

Quranic interpretations


There are several verses in the Qur'an
Qur'an
The Quran , also transliterated Qur'an, Koran, Alcoran, Qur’ān, Coran, Kuran, and al-Qur’ān, is the central religious text of Islam, which Muslims consider the verbatim word of God . It is regarded widely as the finest piece of literature in the Arabic language...

 (610-632) which some medieval and modern writers have interpreted as foreshadowing modern cosmological
Cosmology
Cosmology is the discipline that deals with the nature of the Universe as a whole. Cosmologists seek to understand the origin, evolution, structure, and ultimate fate of the Universe at large, as well as the natural laws that keep it in order...

 theories. An early example of this can be seen in the work of the Islamic theologian Fakhr al-Din al-Razi
Fakhr al-Din al-Razi
Abu Abdullah Muhammad ibn Umar ibn al-Husayn al-Taymi al-Bakri al-Tabaristani Fakhr al-Din al-Razi , most commonly known as Fakhruddin Razi was a well-known Persian Sunni Muslim theologian and philosopher....

 (1149–1209), in dealing with his conception of physics and the physical world in his Matalib. He discusses Islamic cosmology, criticizes the idea of the Earth's centrality
Geocentric model
In astronomy, the geocentric model , is the superseded theory that the Earth is the center of the universe, and that all other objects orbit around it. This geocentric model served as the predominant cosmological system in many ancient civilizations such as ancient Greece...

 within the universe, and explores "the notion of the existence of a multiverse
Multiverse
The multiverse is the hypothetical set of multiple possible universes that together comprise all of reality.Multiverse may also refer to:-In fiction:* Multiverse , the fictional multiverse used by DC Comics...

 in the context of his commentary" on the Qur'anic verse, "All praise belongs to God, Lord of the Worlds." He raises the question of whether the term "worlds" in this verse refers to "multiple world
World
World is a common name for the whole of human civilization, specifically human experience, history, or the human condition in general, worldwide, i.e. anywhere on Earth....

s within this single universe
Universe
The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

 or cosmos
Cosmos
In the general sense, a cosmos is an orderly or harmonious system. It originates from the Greek term κόσμος , meaning "order" or "ornament" and is antithetical to the concept of chaos. Today, the word is generally used as a synonym of the word Universe . The word cosmos originates from the same root...

, or to many other universes or a multiverse beyond this known universe." He rejects the Aristotelian view of a single world or universe in favour of the existence of multiple worlds and universes, a view that he believed to be supported by the Qur'an and by the Ash'ari
Ash'ari
The Ashʿari theology is a school of early Muslim speculative theology founded by the theologian Abu al-Hasan al-Ash'ari...

 theory of atomism
Atomism
Atomism is a natural philosophy that developed in several ancient traditions. The atomists theorized that the natural world consists of two fundamental parts: indivisible atoms and empty void.According to Aristotle, atoms are indestructible and immutable and there are an infinite variety of shapes...

.

Cosmology in the medieval Islamic world


Cosmology was studied extensively in the Muslim world
Muslim world
The term Muslim world has several meanings. In a religious sense, it refers to those who adhere to the teachings of Islam, referred to as Muslims. In a cultural sense, it refers to Islamic civilization, inclusive of non-Muslims living in that civilization...

 during what is known as the Islamic Golden Age
Islamic Golden Age
During the Islamic Golden Age philosophers, scientists and engineers of the Islamic world contributed enormously to technology and culture, both by preserving earlier traditions and by adding their own inventions and innovations...

 from the 7th to 15th centuries.

There are exactly seven verses in the Quran that specify that there are seven heavens.
One verse says that each heaven or sky has its own order, possibly meaning laws of nature. Another verse says after mentioning the seven heavens "and similar earths".

In 850, al-Farghani wrote Kitab fi Jawani ("A compendium of the science of stars"). The book primarily gave a summary of Ptolemic cosmography
Cosmography
Cosmography is the science that maps the general features of the universe, describing both heaven and Earth...

. However, it also corrected Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

's Almagest
Almagest
The Almagest is a 2nd-century mathematical and astronomical treatise on the apparent motions of the stars and planetary paths. Written in Greek by Claudius Ptolemy, a Roman era scholar of Egypt,...

 based on findings of earlier Iranian
Iranian peoples
The Iranian peoples are an Indo-European ethnic-linguistic group, consisting of the speakers of Iranian languages, a major branch of the Indo-European language family, as such forming a branch of Indo-European-speaking peoples...

 astronomers. Al-Farghani gave revised values for the obliquity
Axial tilt
In astronomy, axial tilt is the angle between an object's rotational axis, and a line perpendicular to its orbital plane...

 of the ecliptic
Ecliptic
The ecliptic is the plane of the earth's orbit around the sun. In more accurate terms, it is the intersection of the celestial sphere with the ecliptic plane, which is the geometric plane containing the mean orbit of the Earth around the Sun...

, the precession
Precession
Precession is a change in the orientation of the rotation axis of a rotating body. It can be defined as a change in direction of the rotation axis in which the second Euler angle is constant...

al 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
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

.

Cosmography


ʿAjā'ib al-makhlūqāt wa gharā'ib al-mawjūdāt is an important work of cosmography
Cosmography
Cosmography is the science that maps the general features of the universe, describing both heaven and Earth...

 by Zakariya ibn Muhammad ibn Mahmud Abu Yahya al-Qazwini
Zakariya al-Qazwini
Abu Yahya Zakariya' ibn Muhammad al-Qazwini , was a Persian physician, astronomer, geographer and proto-science fiction writer....

 who was born in Qazwin year 600 (AH
Islamic calendar
The Hijri calendar , also known as the Muslim calendar or Islamic calendar , is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to date events in many Muslim countries , and used by Muslims everywhere to determine the proper day on which to celebrate Islamic...

 (1203 AD).

Temporal finitism


In contrast to ancient Greek philosophers
Greek philosophy
Ancient Greek philosophy arose in the 6th century BCE and continued through the Hellenistic period, at which point Ancient Greece was incorporated in the Roman Empire...

 who believed that the universe
Universe
The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

 had an infinite past with no beginning, medieval philosophers
Medieval philosophy
Medieval philosophy is the philosophy in the era now known as medieval or the Middle Ages, the period roughly extending from the fall of the Western Roman Empire in the fifth century AD to the Renaissance in the sixteenth century...

 and theologians
Theology
Theology is the systematic and rational study of religion and its influences and of the nature of religious truths, or the learned profession acquired by completing specialized training in religious studies, usually at a university or school of divinity or seminary.-Definition:Augustine of Hippo...

 developed the concept of the universe having a finite past with a beginning (see Temporal finitism
Temporal finitism
Temporal finitism is the idea that time is finite. The context of the idea is the pre-modern era, before mathematicians had understood the concept of infinity and before physical cosmology....

). This view was inspired by the creation myth shared by the three Abrahamic religions
Abrahamic religions
Abrahamic religions are the monotheistic faiths emphasizing and tracing their common origin to Abraham or recognizing a spiritual tradition identified with him...

: Judaism
Judaism
Judaism ) is the "religion, philosophy, and way of life" of the Jewish people...

, Christianity
Christianity
Christianity is a monotheistic religion based on the life and teachings of Jesus as presented in canonical gospels and other New Testament writings...

 and Islam
Islam
Islam . The most common are and .   : Arabic pronunciation varies regionally. The first vowel ranges from ~~. The second vowel ranges from ~~~...

. The Christian philosopher
Christian philosophy
Christian philosophy may refer to any development in philosophy that is characterised by coming from a Christian tradition.- Origins of Christian philosophy :...

, John Philoponus
John Philoponus
John Philoponus , also known as John the Grammarian or John of Alexandria, was a Christian and Aristotelian commentator and the author of a considerable number of philosophical treatises and theological works...

, presented the first such argument against the ancient Greek notion of an infinite past. His arguments were adopted by many most notably; early Muslim philosopher
Early Islamic philosophy
Early Islamic philosophy or classical Islamic philosophy is a period of intense philosophical development beginning in the 2nd century AH of the Islamic calendar and lasting until the 6th century AH...

, Al-Kindi
Al-Kindi
' , known as "the Philosopher of the Arabs", was a Muslim Arab philosopher, mathematician, physician, and musician. Al-Kindi was the first of the Muslim peripatetic philosophers, and is unanimously hailed as the "father of Islamic or Arabic philosophy" for his synthesis, adaptation and promotion...

 (Alkindus); the Jewish philosopher
Jewish philosophy
Jewish philosophy , includes all philosophy carried out by Jews, or, in relation to the religion of Judaism. Jewish philosophy, until modern Enlightenment and Emancipation, was pre-occupied with attempts to reconcile coherent new ideas into the tradition of Rabbinic Judaism; thus organizing...

, Saadia Gaon
Saadia Gaon
Saʻadiah ben Yosef Gaon was a prominent rabbi, Jewish philosopher, and exegete of the Geonic period.The first important rabbinic figure to write extensively in Arabic, he is considered the founder of Judeo-Arabic literature...

 (Saadia ben Joseph); and the Muslim theologian
Islamic theology
Islamic theology is a branch of Islamic studies regarding the beliefs associated with the Islamic faith. Any religious belief system, or creed, can be considered an example of aqidah. However, this term has taken a significant technical usage in Islamic history and theology, denoting those...

, Al-Ghazali
Al-Ghazali
Abu Hāmed Mohammad ibn Mohammad al-Ghazzālī , known as Algazel to the western medieval world, born and died in Tus, in the Khorasan province of Persia was a Persian Muslim theologian, jurist, philosopher, and mystic....

 (Algazel). They used two "logical" arguments against an infinite past, the first being the "argument from the impossibility of the existence of an actual infinite", which states:
"An actual infinite cannot exist."
"An infinite temporal regress of events is an actual infinite."
"∴ An infinite temporal regress of events cannot exist."


The second argument, the "argument from the impossibility of completing an actual infinite by successive addition", states:
"An actual infinite cannot be completed by successive addition."
"The temporal series of past events has been completed by successive addition."
"∴ The temporal series of past events cannot be an actual infinite."


Both arguments were adopted by later Christian philosophers and theologians, and the second argument in particular became more famous after it was adopted by Immanuel Kant
Immanuel Kant
Immanuel Kant was a German philosopher from Königsberg , researching, lecturing and writing on philosophy and anthropology at the end of the 18th Century Enlightenment....

 in his thesis of the first antimony concerning time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

.

Galaxy observation


The Persian astronomer Alhazen (965–1037) made the first attempt at observing and measuring the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...

's parallax
Parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek παράλλαξις , meaning "alteration"...

, and he thus "determined that because the Milky Way had no parallax, it was very remote from the earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 and did not belong to the atmosphere." The Persian
Persian people
The Persian people are part of the Iranian peoples who speak the modern Persian language and closely akin Iranian dialects and languages. The origin of the ethnic Iranian/Persian peoples are traced to the Ancient Iranian peoples, who were part of the ancient Indo-Iranians and themselves part of...

 astronomer Abū Rayhān al-Bīrūnī (973–1048) proposed the Milky Way galaxy
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...

 to be "a collection of countless fragments of the nature of nebulous stars." The Andalusian
Al-Andalus
Al-Andalus was the Arabic name given to a nation and territorial region also commonly referred to as Moorish Iberia. The name describes parts of the Iberian Peninsula and Septimania governed by Muslims , at various times in the period between 711 and 1492, although the territorial boundaries...

 astronomer Ibn Bajjah
Ibn Bajjah
Abū-Bakr Muhammad ibn Yahya ibn al-Sāyigh , known as Ibn Bājjah , was an Andalusian polymath: an astronomer, logician, musician, philosopher, physician, physicist, psychologist, botanist, poet and scientist. He was known in the West by his Latinized name, Avempace...

 ("Avempace", d. 1138) proposed that the Milky Way was made up of many stars which almost touched one another and appeared to be a continuous image due to the effect of refraction
Refraction
Refraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon . The phenomenon is mainly in governance to the law of conservation of energy. The proper explanation would be that due to change of medium, the phase velocity of the wave is changed...

 from sublunary material, citing his observation of the conjunction of Jupiter and Mars on 500 AH
Islamic calendar
The Hijri calendar , also known as the Muslim calendar or Islamic calendar , is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to date events in many Muslim countries , and used by Muslims everywhere to determine the proper day on which to celebrate Islamic...

 (1106/1107 AD) as evidence. Ibn Qayyim Al-Jawziyya (1292–1350) proposed the Milky Way galaxy to be "a myriad of tiny stars packed together in the sphere of the fixed stars".

In the 10th century, the Persian astronomer Abd al-Rahman al-Sufi (known in the West as Azophi) made the earliest recorded observation of the Andromeda Galaxy
Andromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...

, describing it as a "small cloud". Al-Sufi also identified the Large Magellanic Cloud
Large Magellanic Cloud
The Large Magellanic Cloud is a nearby irregular galaxy, and is a satellite of the Milky Way. At a distance of slightly less than 50 kiloparsecs , the LMC is the third closest galaxy to the Milky Way, with the Sagittarius Dwarf Spheroidal and Canis Major Dwarf Galaxy lying closer to the center...

, which is visible from Yemen
Yemen
The Republic of Yemen , commonly known as Yemen , is a country located in the Middle East, occupying the southwestern to southern end of the Arabian Peninsula. It is bordered by Saudi Arabia to the north, the Red Sea to the west, and Oman to the east....

, though not from Isfahan; it was not seen by Europeans until Magellan
Ferdinand Magellan
Ferdinand Magellan was a Portuguese explorer. He was born in Sabrosa, in northern Portugal, and served King Charles I of Spain in search of a westward route to the "Spice Islands" ....

's voyage in the 16th century. These were the first galaxies other than the Milky Way to be observed from Earth. Al-Sufi published his findings in his Book of Fixed Stars
Book of Fixed Stars
The Book of Fixed Stars is an astronomical text written by Abd al-Rahman al-Sufi around 964. The book was written in Arabic, although the author himself was Persian...

 in 964.

Possible worlds


Al-Ghazali
Al-Ghazali
Abu Hāmed Mohammad ibn Mohammad al-Ghazzālī , known as Algazel to the western medieval world, born and died in Tus, in the Khorasan province of Persia was a Persian Muslim theologian, jurist, philosopher, and mystic....

, in The Incoherence of the Philosophers
The Incoherence of the Philosophers
The Incoherence of the Philosophers is the title of a landmark 11th century polemic by the Sufi sympathetic Imam Al-Ghazali of the Asharite school of Islamic theology criticizing the Avicennian school of early Islamic philosophy...

, defends the Ash'ari
Ash'ari
The Ashʿari theology is a school of early Muslim speculative theology founded by the theologian Abu al-Hasan al-Ash'ari...

 doctrine of a created universe
Islamic creationism
Islamic views on evolution refers to varying Muslim beliefs on how the life came to be. Muslims acknowledge God as the Creator, as explained in the Qur'an. Other than that, Muslim views on evolution vary...

 that is temporally finite
Temporal finitism
Temporal finitism is the idea that time is finite. The context of the idea is the pre-modern era, before mathematicians had understood the concept of infinity and before physical cosmology....

, against the Aristotelian
Aristotelianism
Aristotelianism is a tradition of philosophy that takes its defining inspiration from the work of Aristotle. The works of Aristotle were initially defended by the members of the Peripatetic school, and, later on, by the Neoplatonists, who produced many commentaries on Aristotle's writings...

 doctrine of an eternal
Eternity
While in the popular mind, eternity often simply means existence for a limitless amount of time, many have used it to refer to a timeless existence altogether outside time. By contrast, infinite temporal existence is then called sempiternity. Something eternal exists outside time; by contrast,...

 universe. In doing so, he proposed the modal
Modal realism
Modal realism is the view, notably propounded by David Kellogg Lewis, that all possible worlds are as real as the actual world. It is based on the following tenets: possible worlds exist; possible worlds are not different in kind from the actual world; possible worlds are irreducible entities; the...

 theory of possible world
Possible world
In philosophy and logic, the concept of a possible world is used to express modal claims. The concept of possible worlds is common in contemporary philosophical discourse and has also been disputed.- Possibility, necessity, and contingency :...

s, arguing that their actual world is the best of all possible worlds
Best of all possible worlds
The phrase "the best of all possible worlds" was coined by the German polymath Gottfried Leibniz in his 1710 work Essais de Théodicée sur la bonté de Dieu, la liberté de l'homme et l'origine du mal...

 from among all the alternate timelines and world histories
World History
World History, Global History or Transnational history is a field of historical study that emerged as a distinct academic field in the 1980s. It examines history from a global perspective...

 that God could have possibly created. His theory parallels that of Duns Scotus
Duns Scotus
Blessed John Duns Scotus, O.F.M. was one of the more important theologians and philosophers of the High Middle Ages. He was nicknamed Doctor Subtilis for his penetrating and subtle manner of thought....

 in the 14th century. While it is uncertain whether Al-Ghazali had any influence on Scotus, they both may have derived their theory from their readings of Avicenna
Avicenna
Abū ʿAlī al-Ḥusayn ibn ʿAbd Allāh ibn Sīnā , commonly known as Ibn Sīnā or by his Latinized name Avicenna, was a Persian polymath, who wrote almost 450 treatises on a wide range of subjects, of which around 240 have survived...

's Metaphysics.

Multiversal cosmology


Fakhr al-Din al-Razi
Fakhr al-Din al-Razi
Abu Abdullah Muhammad ibn Umar ibn al-Husayn al-Taymi al-Bakri al-Tabaristani Fakhr al-Din al-Razi , most commonly known as Fakhruddin Razi was a well-known Persian Sunni Muslim theologian and philosopher....

 (1149–1209), in dealing with his conception of physics and the physical world in his Matalib al-'Aliya, criticizes the idea of the Earth's centrality
Geocentric model
In astronomy, the geocentric model , is the superseded theory that the Earth is the center of the universe, and that all other objects orbit around it. This geocentric model served as the predominant cosmological system in many ancient civilizations such as ancient Greece...

 within the universe and "explores the notion of the existence of a multiverse
Multiverse
The multiverse is the hypothetical set of multiple possible universes that together comprise all of reality.Multiverse may also refer to:-In fiction:* Multiverse , the fictional multiverse used by DC Comics...

 in the context of his commentary" on the Qur'an
Qur'an
The Quran , also transliterated Qur'an, Koran, Alcoran, Qur’ān, Coran, Kuran, and al-Qur’ān, is the central religious text of Islam, which Muslims consider the verbatim word of God . It is regarded widely as the finest piece of literature in the Arabic language...

ic verse, "All praise belongs to God, Lord of the Worlds." He raises the question of whether the term "world
World
World is a common name for the whole of human civilization, specifically human experience, history, or the human condition in general, worldwide, i.e. anywhere on Earth....

s" in this verse refers to "multiple worlds within this single universe
Universe
The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

 or cosmos
Cosmos
In the general sense, a cosmos is an orderly or harmonious system. It originates from the Greek term κόσμος , meaning "order" or "ornament" and is antithetical to the concept of chaos. Today, the word is generally used as a synonym of the word Universe . The word cosmos originates from the same root...

, or to many other universes or a multiverse beyond this known universe." In volume 4 of the Matalib, Al-Razi states:
Al-Razi rejected the Aristotelian
Aristotelianism
Aristotelianism is a tradition of philosophy that takes its defining inspiration from the work of Aristotle. The works of Aristotle were initially defended by the members of the Peripatetic school, and, later on, by the Neoplatonists, who produced many commentaries on Aristotle's writings...

 and Avicennian notions of a single universe revolving around a single world. He describes the main arguments against the existence of multiple worlds or universes, pointing out their weaknesses and refuting them. This rejection arose from his affirmation of atomism
Atomism
Atomism is a natural philosophy that developed in several ancient traditions. The atomists theorized that the natural world consists of two fundamental parts: indivisible atoms and empty void.According to Aristotle, atoms are indestructible and immutable and there are an infinite variety of shapes...

, as advocated by the Ash'ari
Ash'ari
The Ashʿari theology is a school of early Muslim speculative theology founded by the theologian Abu al-Hasan al-Ash'ari...

 school of Islamic theology
Islamic theology
Islamic theology is a branch of Islamic studies regarding the beliefs associated with the Islamic faith. Any religious belief system, or creed, can be considered an example of aqidah. However, this term has taken a significant technical usage in Islamic history and theology, denoting those...

, which entails the existence of vacant space in which the atoms move, combine and separate. He discussed in greater detail the void
Void (astronomy)
In astronomy, voids are the empty spaces between filaments, the largest-scale structures in the Universe, that contain very few, or no, galaxies. They were first discovered in 1978 during a pioneering study by Stephen Gregory and Laird A. Thompson at the Kitt Peak National Observatory...

, the empty space between stars and constellations in the Universe
Universe
The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

, in volume 5 of the Matalib. He argued that there exists an infinite outer space
Outer space
Outer space is the void that exists between celestial bodies, including the Earth. It is not completely empty, but consists of a hard vacuum containing a low density of particles: predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, and neutrinos....

 beyond the known world, and that God has the power to fill the vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...

 with an infinite number of universes.

Refutations of astrology


The study of astrology was refuted by several Muslim writers at the time, including al-Farabi
Al-Farabi
' known in the West as Alpharabius , was a scientist and philosopher of the Islamic world...

, Ibn al-Haytham, Avicenna
Avicenna
Abū ʿAlī al-Ḥusayn ibn ʿAbd Allāh ibn Sīnā , commonly known as Ibn Sīnā or by his Latinized name Avicenna, was a Persian polymath, who wrote almost 450 treatises on a wide range of subjects, of which around 240 have survived...

, Biruni and Averroes
Averroes
' , better known just as Ibn Rushd , and in European literature as Averroes , was a Muslim polymath; a master of Aristotelian philosophy, Islamic philosophy, Islamic theology, Maliki law and jurisprudence, logic, psychology, politics, Arabic music theory, and the sciences of medicine, astronomy,...

. Their reasons for refuting astrology were often due to both scientific (the methods used by astrologers being conjectural rather than empirical
Empirical
The word empirical denotes information gained by means of observation or experimentation. Empirical data are data produced by an experiment or observation....

) and religious (conflicts with orthodox Islamic scholars
Ulema
Ulama , also spelt ulema, refers to the educated class of Muslim legal scholars engaged in the several fields of Islamic studies. They are best known as the arbiters of shari‘a law...

) reasons.

Ibn Qayyim Al-Jawziyya (1292–1350), in his Miftah Dar al-SaCadah, used empirical
Empirical
The word empirical denotes information gained by means of observation or experimentation. Empirical data are data produced by an experiment or observation....

 arguments in astronomy in order to refute the practice of astrology and divination
Divination
Divination is the attempt to gain insight into a question or situation by way of an occultic standardized process or ritual...

. He recognized that the star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

s are much larger than the planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...

s, and thus argued:
Al-Jawziyya also recognized the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...

 galaxy
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...

 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."

Early heliocentric models


The Babylonian astronomer, Seleucus of Seleucia
Seleucus of Seleucia
Seleucus of Seleucia was a Hellenistic astronomer and philosopher. Coming from Seleucia on the Tigris, the capital of the Seleucid empire, or, alternatively, Seleukia on the Red Sea, he is best known as a proponent of heliocentrism and for his theory of the origin of tides.- Heliocentric theory...

, who advocated a heliocentric
Heliocentrism
Heliocentrism, or heliocentricism, is the astronomical model in which the Earth and planets revolve around a stationary Sun at the center of the universe. The word comes from the Greek . Historically, heliocentrism was opposed to geocentrism, which placed the Earth at the center...

 model in the 2nd century BC, wrote a work that was later translated into Arabic. A fragment of his work has survived only in Arabic translation, which was later referred to by the Persian philosopher
Iranian philosophy
Iranian philosophy or Persian philosophy can be traced back as far as to Old Iranian philosophical traditions and thoughts which originated in ancient Indo-Iranian roots and were considerably influenced by Zarathustra's teachings...

 Muhammad ibn Zakariya al-Razi (865-925).

In the late ninth century, Ja'far ibn Muhammad Abu Ma'shar al-Balkhi
Ja'far ibn Muhammad Abu Ma'shar al-Balkhi
Abū Maʿshar, Jaʿfar ibn Muḥammad al-Balkhī , was a Persian astrologer, astronomer, and Islamic philosopher, thought to be the greatest astrologer of the Abbasid court in Baghdad...

 (Albumasar) developed a planetary model which some have interpreted as a heliocentric model
Heliocentrism
Heliocentrism, or heliocentricism, is the astronomical model in which the Earth and planets revolve around a stationary Sun at the center of the universe. The word comes from the Greek . Historically, heliocentrism was opposed to geocentrism, which placed the Earth at the center...

. This is due to his orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...

al revolutions of the planets being given as heliocentric revolutions rather than geocentric
Geocentric model
In astronomy, the geocentric model , is the superseded theory that the Earth is the center of the universe, and that all other objects orbit around it. This geocentric model served as the predominant cosmological system in many ancient civilizations such as ancient Greece...

 revolutions, and the only known planetary theory in which this occurs is in the heliocentric theory. His work on planetary theory has not survived, but his astronomical data was later recorded by al-Hashimi, Abū Rayhān al-Bīrūnī and al-Sijzi
Al-Sijzi
Abu Sa'id Ahmed ibn Mohammed ibn Abd Jalil Sijzi was a Persian astronomer and mathematician from Sistan, a region lying in the south-west of Afghanistan and south-east of Iran....

.

In the early eleventh century, al-Biruni
Al-Biruni
Abū al-Rayḥān Muḥammad ibn Aḥmad al-BīrūnīArabic spelling. . The intermediate form Abū Rayḥān al-Bīrūnī is often used in academic literature...

 had met several Indian scholars who believed in a heliocentric system. In his Indica, he discusses the theories on the Earth's rotation supported by Brahmagupta
Brahmagupta
Brahmagupta was an Indian mathematician and astronomer who wrote many important works on mathematics and astronomy. His best known work is the Brāhmasphuṭasiddhānta , written in 628 in Bhinmal...

 and other Indian astronomers, while in his Canon Masudicus, al-Biruni writes that Aryabhata
Aryabhata
Aryabhata was the first in the line of great mathematician-astronomers from the classical age of Indian mathematics and Indian astronomy...

's followers assigned the first movement from east to west to the Earth and a second movement from west to east to the fixed stars. Al-Biruni also wrote that al-Sijzi
Al-Sijzi
Abu Sa'id Ahmed ibn Mohammed ibn Abd Jalil Sijzi was a Persian astronomer and mathematician from Sistan, a region lying in the south-west of Afghanistan and south-east of Iran....

 also believed the Earth was moving and invented an astrolabe
Astrolabe
An astrolabe is an elaborate inclinometer, historically used by astronomers, navigators, and astrologers. Its many uses include locating and predicting the positions of the Sun, Moon, planets, and stars, determining local time given local latitude and longitude, surveying, triangulation, and to...

 called the "Zuraqi" based on this idea:
In his Indica, al-Biruni briefly refers to his work on the refutation of heliocentrism, the Key of Astronomy, which is now lost:

Early Hay'a program


During this period, a distinctive Islamic system of astronomy flourished. It was Greek tradition to separate mathematical astronomy (as typified by Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

) from philosophical cosmology (as typified by Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

). Muslim scholars developed a program of seeking a physically real configuration (hay'a) of the universe, that would be consistent with both mathematical
Mathematics
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...

 and physical
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

 principles. Within the context of this hay'a tradition, Muslim astronomers began questioning technical details of the Ptolemaic system of astronomy.

Some Muslim astronomers, however, most notably Abū Rayhān al-Bīrūnī and Nasīr al-Dīn al-Tūsī
Nasir al-Din al-Tusi
Khawaja Muḥammad ibn Muḥammad ibn Ḥasan Ṭūsī , better known as Naṣīr al-Dīn al-Ṭūsī , was a Persian polymath and prolific writer: an astronomer, biologist, chemist, mathematician, philosopher, physician, physicist, scientist, theologian and Marja Taqleed...

, discussed whether the Earth moved and considered how this might be consistent with astronomical computations and physical systems. Several other Muslim astronomers, most notably those following the Maragha school
Maragheh observatory
Maragheh observatory is an astronomical observatory which was established in 1259 CE by Nasir al-Din al-Tusi, an Iranian scientist and astronomer...

 of astronomy, developed non-Ptolemaic planetary models within a geocentric context that were later adapted by the Copernican model
Copernican heliocentrism
Copernican heliocentrism is the name given to the astronomical model developed by Nicolaus Copernicus and published in 1543. It positioned the Sun near the center of the Universe, motionless, with Earth and the other planets rotating around it in circular paths modified by epicycles and at uniform...

 in a heliocentric
Heliocentrism
Heliocentrism, or heliocentricism, is the astronomical model in which the Earth and planets revolve around a stationary Sun at the center of the universe. The word comes from the Greek . Historically, heliocentrism was opposed to geocentrism, which placed the Earth at the center...

 context.

Between 1025 and 1028, Ibn al-Haytham (Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

ized 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
Geocentric model
In astronomy, the geocentric model , is the superseded theory that the Earth is the center of the universe, and that all other objects orbit around it. This geocentric model served as the predominant cosmological system in many ancient civilizations such as ancient Greece...

, he was the first to criticize Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

's astronomical system, which he criticized on empirical
Empirical
The word empirical denotes information gained by means of observation or experimentation. Empirical data are data produced by an experiment or observation....

, observation
Observation
Observation is either an activity of a living being, such as a human, consisting of receiving knowledge of the outside world through the senses, or the recording of data using scientific instruments. The term may also refer to any data collected during this activity...

al and experiment
Experiment
An experiment is a methodical procedure carried out with the goal of verifying, falsifying, or establishing the validity of a hypothesis. Experiments vary greatly in their goal and scale, but always rely on repeatable procedure and logical analysis of the results...

al grounds, and for relating actual physical motions to imaginary mathematical points, lines and circles. Ibn al-Haytham developed a physical structure of the Ptolemaic system in his Treatise on the configuration of the World, or Maqâlah fî hay'at al-‛âlam, which became an influential work in the hay'a tradition. In his Epitome of Astronomy, he insisted that the heavenly bodies "were accountable to the laws of physics
Physical law
A physical law or scientific law is "a theoretical principle deduced from particular facts, applicable to a defined group or class of phenomena, and expressible by the statement that a particular phenomenon always occurs if certain conditions be present." Physical laws are typically conclusions...

."

In 1038, Ibn al-Haytham described the first non-Ptolemaic configuration in The Model of the Motions. His reform was not concerned with cosmology
Cosmology
Cosmology is the discipline that deals with the nature of the Universe as a whole. Cosmologists seek to understand the origin, evolution, structure, and ultimate fate of the Universe at large, as well as the natural laws that keep it in order...

, as he developed a systematic study of celestial kinematics
Kinematics
Kinematics is the branch of classical mechanics that describes the motion of bodies and systems without consideration of the forces that cause the motion....

 that was completely geometric
Geometry
Geometry arose as the field of knowledge dealing with spatial relationships. Geometry was one of the two fields of pre-modern mathematics, the other being the study of numbers ....

. This in turn led to innovative developments in infinitesimal
Infinitesimal
Infinitesimals have been used to express the idea of objects so small that there is no way to see them or to measure them. The word infinitesimal comes from a 17th century Modern Latin coinage infinitesimus, which originally referred to the "infinite-th" item in a series.In common speech, an...

 geometry
Geometry
Geometry arose as the field of knowledge dealing with spatial relationships. Geometry was one of the two fields of pre-modern mathematics, the other being the study of numbers ....

. His reformed model was the first to reject the equant
Equant
Equant is a mathematical concept developed by Claudius Ptolemy in the 2nd century AD to account for the observed motion of heavenly bodies....

 and eccentrics, separate natural philosophy
Natural philosophy
Natural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...

 from astronomy, free celestial kinematics from cosmology, and reduce physical entities to geometrical entities. The model also propounded the Earth's rotation about its axis, and the centres of motion were geometrical points without any physical significance, like Johannes Kepler
Johannes Kepler
Johannes Kepler was a German mathematician, astronomer and astrologer. A key figure in the 17th century scientific revolution, he is best known for his eponymous laws of planetary motion, codified by later astronomers, based on his works Astronomia nova, Harmonices Mundi, and Epitome of Copernican...

's model centuries later. Ibn al-Haytham also describes an early version of Occam's razor
Occam's razor
Occam's razor, also known as Ockham's razor, and sometimes expressed in Latin as lex parsimoniae , is a principle that generally recommends from among competing hypotheses selecting the one that makes the fewest new assumptions.-Overview:The principle is often summarized as "simpler explanations...

, where he employs only minimal hypotheses regarding the properties that characterize astronomical motions, as he attempts to eliminate from his planetary model the cosmological
Cosmology
Cosmology is the discipline that deals with the nature of the Universe as a whole. Cosmologists seek to understand the origin, evolution, structure, and ultimate fate of the Universe at large, as well as the natural laws that keep it in order...

 hypotheses that cannot be observed from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

.

In 1030, Abū al-Rayhān al-Bīrūnī discussed the Indian planetary theories of Aryabhata
Aryabhata
Aryabhata was the first in the line of great mathematician-astronomers from the classical age of Indian mathematics and Indian astronomy...

, Brahmagupta
Brahmagupta
Brahmagupta was an Indian mathematician and astronomer who wrote many important works on mathematics and astronomy. His best known work is the Brāhmasphuṭasiddhānta , written in 628 in Bhinmal...

 and Varahamihira
Varahamihira
Varāhamihira , also called Varaha or Mihira, was an Indian astronomer, mathematician, and astrologer who lived in Ujjain...

 in his Ta'rikh al-Hind (Latinized as Indica). Biruni stated that Brahmagupta
Brahmagupta
Brahmagupta was an Indian mathematician and astronomer who wrote many important works on mathematics and astronomy. His best known work is the Brāhmasphuṭasiddhānta , written in 628 in Bhinmal...

 and others consider that the earth rotates on its axis and Biruni noted that this does not create any mathematical problems. Abu Said al-Sijzi
Al-Sijzi
Abu Sa'id Ahmed ibn Mohammed ibn Abd Jalil Sijzi was a Persian astronomer and mathematician from Sistan, a region lying in the south-west of Afghanistan and south-east of Iran....

, a contemporary of al-Biruni, suggested the possible heliocentric movement of the Earth around the Sun, which al-Biruni did not reject. Al-Biruni agreed with the Earth's rotation about its own axis, and while he was initially neutral regarding the heliocentric
Heliocentrism
Heliocentrism, or heliocentricism, is the astronomical model in which the Earth and planets revolve around a stationary Sun at the center of the universe. The word comes from the Greek . Historically, heliocentrism was opposed to geocentrism, which placed the Earth at the center...

 and geocentric model
Geocentric model
In astronomy, the geocentric model , is the superseded theory that the Earth is the center of the universe, and that all other objects orbit around it. This geocentric model served as the predominant cosmological system in many ancient civilizations such as ancient Greece...

s, he considered heliocentrism to be a philosophical problem. He remarked that if the Earth rotates on its axis and moves around the Sun, it would remain consistent with his astronomical parameters:

Andalusian Revolt


In the 11th-12th centuries, astronomers in al-Andalus
Al-Andalus
Al-Andalus was the Arabic name given to a nation and territorial region also commonly referred to as Moorish Iberia. The name describes parts of the Iberian Peninsula and Septimania governed by Muslims , at various times in the period between 711 and 1492, although the territorial boundaries...

 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
Geocentric model
In astronomy, the geocentric model , is the superseded theory that the Earth is the center of the universe, and that all other objects orbit around it. This geocentric model served as the predominant cosmological system in many ancient civilizations such as ancient Greece...

. Like Ibn al-Haytham's critique, the anonymous Andalusian work, al-Istidrak ala Batlamyus (Recapitulation regarding Ptolemy), included a list of objections to Ptolemic astronomy. This marked the beginning of the Andalusian school's revolt against Ptolemaic astronomy, otherwise known as the "Andalusian Revolt".

In the 12th century, Averroes
Averroes
' , better known just as Ibn Rushd , and in European literature as Averroes , was a Muslim polymath; a master of Aristotelian philosophy, Islamic philosophy, Islamic theology, Maliki law and jurisprudence, logic, psychology, politics, Arabic music theory, and the sciences of medicine, astronomy,...

 rejected the eccentric deferents
Deferent and epicycle
In the Ptolemaic system of astronomy, the epicycle was a geometric model used to explain the variations in speed and direction of the apparent motion of the Moon, Sun, and planets...

 introduced by Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

. He rejected the Ptolemaic model and instead argued for a strictly concentric
Concentric
Concentric objects share the same center, axis or origin with one inside the other. Circles, tubes, cylindrical shafts, disks, and spheres may be concentric to one another...

 model of the universe. He wrote the following criticism on the Ptolemaic model of planetary motion:
Averroes' contemporary, Maimonides
Maimonides
Moses ben-Maimon, called Maimonides and also known as Mūsā ibn Maymūn in Arabic, or Rambam , was a preeminent medieval Jewish philosopher and one of the greatest Torah scholars and physicians of the Middle Ages...

, wrote the following on the planetary model proposed by Ibn Bajjah
Ibn Bajjah
Abū-Bakr Muhammad ibn Yahya ibn al-Sāyigh , known as Ibn Bājjah , was an Andalusian polymath: an astronomer, logician, musician, philosopher, physician, physicist, psychologist, botanist, poet and scientist. He was known in the West by his Latinized name, Avempace...

 (Avempace):
Ibn Bajjah also proposed the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...

 galaxy
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...

 to be made up of many stars but that it appears to be a continuous image due to the effect of refraction
Refraction
Refraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon . The phenomenon is mainly in governance to the law of conservation of energy. The proper explanation would be that due to change of medium, the phase velocity of the wave is changed...

 in the Earth's atmosphere
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

. Later in the 12th century, his successors Ibn Tufail
Ibn Tufail
Ibn Tufail was an Andalusian Muslim polymath: an Arabic writer, novelist, Islamic philosopher, Islamic theologian, physician, vizier,...

 and Nur Ed-Din Al Betrugi
Nur Ed-Din Al Betrugi
Nur ad-Din al-Bitruji was an astronomer and a Qadi from Al-Andalus...

 (Alpetragius) were the first to propose planetary models without any equant
Equant
Equant is a mathematical concept developed by Claudius Ptolemy in the 2nd century AD to account for the observed motion of heavenly bodies....

, epicycles or eccentrics
Deferent and epicycle
In the Ptolemaic system of astronomy, the epicycle was a geometric model used to explain the variations in speed and direction of the apparent motion of the Moon, Sun, and planets...

. Their configurations, however, were not accepted due to the numerical predictions of the planetary positions in their models being less accurate than that of the Ptolemaic model, mainly because they followed Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

's notion of perfectly uniform circular motion
Uniform circular motion
In physics, uniform circular motion describes the motion of a body traversing a circular path at constant speed. The distance of the body from the axis of rotation remains constant at all times. Though the body's speed is constant, its velocity is not constant: velocity, a vector quantity, depends...

.

Maragha Revolution


The "Maragha Revolution" refers to the Maragheh
Maragheh
Maragheh also Romanized as Marāgheh and Marāghen) is a city in and the capital of Maragheh County, East Azerbaijan Province, Iran. At the 2006 census, its population was 146,405, in 38,891 families....

 school's revolution
Revolution
A revolution is a fundamental change in power or organizational structures that takes place in a relatively short period of time.Aristotle described two types of political revolution:...

 against Ptolemaic astronomy. The "Maragha school" was an astronomical tradition beginning in the Maragheh observatory
Maragheh observatory
Maragheh observatory is an astronomical observatory which was established in 1259 CE by Nasir al-Din al-Tusi, an Iranian scientist and astronomer...

 and continuing with astronomers from Damascus
Damascus
Damascus , commonly known in Syria as Al Sham , and as the City of Jasmine , is the capital and the second largest city of Syria after Aleppo, both are part of the country's 14 governorates. In addition to being one of the oldest continuously inhabited cities in the world, Damascus is a major...

 and Samarkand
Samarkand
Although a Persian-speaking region, it was not united politically with Iran most of the times between the disintegration of the Seleucid Empire and the Arab conquest . In the 6th century it was within the domain of the Turkic kingdom of the Göktürks.At the start of the 8th century Samarkand came...

. Like their Andalusian predecessors, the Maragha astronomers attempted to solve the equant
Equant
Equant is a mathematical concept developed by Claudius Ptolemy in the 2nd century AD to account for the observed motion of heavenly bodies....

 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
Empirical
The word empirical denotes information gained by means of observation or experimentation. Empirical data are data produced by an experiment or observation....

 observation
Observation
Observation is either an activity of a living being, such as a human, consisting of receiving knowledge of the outside world through the senses, or the recording of data using scientific instruments. The term may also refer to any data collected during this activity...

s. The most important of the Maragha astronomers included Mo'ayyeduddin Urdi
Mo'ayyeduddin Urdi
Mu’ayyad al-Din al-’Urdi was an Kurdish Muslim astronomer, mathematician, architect and engineer working at the Maragheh observatory...

 (d. 1266), Nasīr al-Dīn al-Tūsī
Nasir al-Din al-Tusi
Khawaja Muḥammad ibn Muḥammad ibn Ḥasan Ṭūsī , better known as Naṣīr al-Dīn al-Ṭūsī , was a Persian polymath and prolific writer: an astronomer, biologist, chemist, mathematician, philosopher, physician, physicist, scientist, theologian and Marja Taqleed...

 (1201–1274), Najm al-Dīn al-Qazwīnī al-Kātibī
Najm al-Dīn al-Qazwīnī al-Kātibī
Najm al-Dīn al-Qazwīnī al-Kātibī was a Persian Islamic philosopher and logician of the Shafi`i school. A student of Nasir al-Din al-Tusi, he is the author of two major works, one on logic, Al-Risala al-Shamsiyya, and one on metaphysics and the natural sciences, Hikmat al-'Ain.-Logic:His work on...

 (d. 1277), Qutb al-Din al-Shirazi
Qutb al-Din al-Shirazi
Qotb al-Din Shirazi or Qutb al-Din al-Shirazi was a 13th century Persian Muslim polymath and Persian poet who made contributions astronomy, mathematics, medicine, physics, music theory, philosophy and Sufism.- Biography :...

 (1236–1311), Sadr al-Sharia al-Bukhari (c. 1347), Ibn al-Shatir
Ibn al-Shatir
Ala Al-Din Abu'l-Hasan Ali Ibn Ibrahim Ibn al-Shatir was an Arab Muslim astronomer, mathematician, engineer and inventor who worked as muwaqqit at the Umayyad Mosque in Damascus, Syria.-Astronomy:...

 (1304–1375), Ali Qushji (c. 1474), al-Birjandi
Al-Birjandi
Abd Ali ibn Muhammad ibn Husayn Birjandi was a prominent 16th century Persian astronomer, mathematician and physicist who lived in Birjand, Iran.- His works :...

 (d. 1525) and Shams al-Din al-Khafri (d. 1550).

Some have described their achievements in the 13th and 14th centuries as a "Maragha Revolution", "Maragha School Revolution", or "Scientific Revolution
Scientific revolution
The Scientific Revolution is an era associated primarily with the 16th and 17th centuries during which new ideas and knowledge in physics, astronomy, biology, medicine and chemistry transformed medieval and ancient views of nature and laid the foundations for modern science...

 before the Renaissance
Renaissance
The Renaissance was a cultural movement that spanned roughly the 14th to the 17th century, beginning in Italy in the Late Middle Ages and later spreading to the rest of Europe. The term is also used more loosely to refer to the historical era, but since the changes of the Renaissance were not...

". An important aspect of this revolution included the realization that astronomy should aim to describe the behavior of physical bodies
Physical body
In physics, a physical body or physical object is a collection of masses, taken to be one...

 in mathematical
Islamic mathematics
In the history of mathematics, mathematics in medieval Islam, often termed Islamic mathematics or Arabic mathematics, covers the body of mathematics preserved and developed under the Islamic civilization between circa 622 and 1600...

 language, and should not remain a mathematical hypothesis
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...

, which would only save the phenomena. The Maragha astronomers also realized that the Aristotelian
On the Heavens
On the Heavens is Aristotle's chief cosmological treatise: it contains his astronomical theory and his ideas on the concrete workings of the terrestrial world...

 view of motion
Motion (physics)
In physics, motion is a change in position of an object with respect to time. Change in action is the result of an unbalanced force. Motion is typically described in terms of velocity, acceleration, displacement and time . An object's velocity cannot change unless it is acted upon by a force, as...

 in the universe being only circular or linear
Linear
In mathematics, a linear map or function f is a function which satisfies the following two properties:* Additivity : f = f + f...

 was not true, as the Tusi-couple
Tusi-couple
The Tusi-couple is a mathematical device in which a small circle rotates inside a larger circle twice the diameter of the smaller circle. Rotations of the circles cause a point on the circumference of the smaller circle to oscillate back and forth in linear motion along a diameter of the larger...

 showed that linear motion could also be produced by applying circular motion
Circular motion
In physics, circular motion is rotation along a circular path or a circular orbit. It can be uniform, that is, with constant angular rate of rotation , or non-uniform, that is, with a changing rate of rotation. The rotation around a fixed axis of a three-dimensional body involves circular motion of...

s only.

Unlike the ancient Greek and Hellenistic astronomers who were not concerned with the coherence between the mathematical and physical principles of a planetary theory, Islamic astronomers insisted on the need to match the mathematics with the real world surrounding them, which gradually evolved from a reality based on Aristotelian physics
Aristotelian physics
Aristotelian Physics the natural sciences, are described in the works of the Greek philosopher Aristotle . In the Physics, Aristotle established general principles of change that govern all natural bodies; both living and inanimate, celestial and terrestrial—including all motion, change in respect...

 to one based on an empirical and mathematical physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

 after the work of Ibn al-Shatir. The Maragha Revolution was thus characterized by a shift away from the philosophical foundations of Aristotelian cosmology
On the Heavens
On the Heavens is Aristotle's chief cosmological treatise: it contains his astronomical theory and his ideas on the concrete workings of the terrestrial world...

 and Ptolemaic astronomy and towards a greater emphasis on the empirical observation and mathematization
Islamic mathematics
In the history of mathematics, mathematics in medieval Islam, often termed Islamic mathematics or Arabic mathematics, covers the body of mathematics preserved and developed under the Islamic civilization between circa 622 and 1600...

 of astronomy and of nature
Nature
Nature, in the broadest sense, is equivalent to the natural world, physical world, or material world. "Nature" refers to the phenomena of the physical world, and also to life in general...

 in general, as exemplified in the works of Ibn al-Shatir, Qushji, al-Birjandi and al-Khafri.

Other achievements of the Maragha school include the first empirical observational evidence for the Earth's rotation on its axis by al-Tusi and Qushji, the separation of natural philosophy
Natural philosophy
Natural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...

 from astronomy by Ibn al-Shatir and Qushji, the rejection of the Ptolemaic model on empirical rather than philosophical grounds by Ibn al-Shatir, and the development of a non-Ptolemaic model by Ibn al-Shatir that was mathematically identical to the heliocentric Copernical model
Copernican heliocentrism
Copernican heliocentrism is the name given to the astronomical model developed by Nicolaus Copernicus and published in 1543. It positioned the Sun near the center of the Universe, motionless, with Earth and the other planets rotating around it in circular paths modified by epicycles and at uniform...

.

Mo'ayyeduddin Urdi
Mo'ayyeduddin Urdi
Mu’ayyad al-Din al-’Urdi was an Kurdish Muslim astronomer, mathematician, architect and engineer working at the Maragheh observatory...

 (d. 1266) was the first of the Maragheh astronomers to develop a non-Ptolemaic model, and he proposed a new theorem, the "Urdi lemma". Nasīr al-Dīn al-Tūsī
Nasir al-Din al-Tusi
Khawaja Muḥammad ibn Muḥammad ibn Ḥasan Ṭūsī , better known as Naṣīr al-Dīn al-Ṭūsī , was a Persian polymath and prolific writer: an astronomer, biologist, chemist, mathematician, philosopher, physician, physicist, scientist, theologian and Marja Taqleed...

 (1201–1274) resolved significant problems in the Ptolemaic system by developing the Tusi-couple
Tusi-couple
The Tusi-couple is a mathematical device in which a small circle rotates inside a larger circle twice the diameter of the smaller circle. Rotations of the circles cause a point on the circumference of the smaller circle to oscillate back and forth in linear motion along a diameter of the larger...

 as an alternative to the physically problematic equant
Equant
Equant is a mathematical concept developed by Claudius Ptolemy in the 2nd century AD to account for the observed motion of heavenly bodies....

 introduced by Ptolemy. Tusi's student Qutb al-Din al-Shirazi
Qutb al-Din al-Shirazi
Qotb al-Din Shirazi or Qutb al-Din al-Shirazi was a 13th century Persian Muslim polymath and Persian poet who made contributions astronomy, mathematics, medicine, physics, music theory, philosophy and Sufism.- Biography :...

 (1236–1311), in his The Limit of Accomplishment concerning Knowledge of the Heavens, discussed the possibility of heliocentrism
Heliocentrism
Heliocentrism, or heliocentricism, is the astronomical model in which the Earth and planets revolve around a stationary Sun at the center of the universe. The word comes from the Greek . Historically, heliocentrism was opposed to geocentrism, which placed the Earth at the center...

. Al-Qazwīnī al-Kātibī, 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.

Ibn al-Shatir
Ibn al-Shatir
Ala Al-Din Abu'l-Hasan Ali Ibn Ibrahim Ibn al-Shatir was an Arab Muslim astronomer, mathematician, engineer and inventor who worked as muwaqqit at the Umayyad Mosque in Damascus, Syria.-Astronomy:...

 (1304–1375) of Damascus
Damascus
Damascus , commonly known in Syria as Al Sham , and as the City of Jasmine , is the capital and the second largest city of Syria after Aleppo, both are part of the country's 14 governorates. In addition to being one of the oldest continuously inhabited cities in the world, Damascus is a major...

, 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
Nicolaus Copernicus
Nicolaus Copernicus was a Renaissance astronomer and the first person to formulate a comprehensive heliocentric cosmology which displaced the Earth from the center of the universe....

 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
Natural philosophy
Natural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...

 or Aristotelian cosmology
Cosmology
Cosmology is the discipline that deals with the nature of the Universe as a whole. Cosmologists seek to understand the origin, evolution, structure, and ultimate fate of the Universe at large, as well as the natural laws that keep it in order...

, but rather to produce a model that was more consistent with empirical
Empirical
The word empirical denotes information gained by means of observation or experimentation. Empirical data are data produced by an experiment or observation....

 observations. For example, it was Ibn al-Shatir's concern for observational accuracy which led him to eliminate the epicycle in the Ptolemaic solar
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 model and all the eccentrics, epicycles and equant in the Ptolemaic lunar
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 model. His model was thus in better agreement with empirical observation
Observation
Observation is either an activity of a living being, such as a human, consisting of receiving knowledge of the outside world through the senses, or the recording of data using scientific instruments. The term may also refer to any data collected during this activity...

s than any previous model, and was also the first that permitted empirical testing
Experiment
An experiment is a methodical procedure carried out with the goal of verifying, falsifying, or establishing the validity of a hypothesis. Experiments vary greatly in their goal and scale, but always rely on repeatable procedure and logical analysis of the results...

. His work thus marked a turning point in astronomy, which may be considered a "Scientific Revolution before the Renaissance". His rectified model was later adapted into a heliocentric model
Copernican heliocentrism
Copernican heliocentrism is the name given to the astronomical model developed by Nicolaus Copernicus and published in 1543. It positioned the Sun near the center of the Universe, motionless, with Earth and the other planets rotating around it in circular paths modified by epicycles and at uniform...

 by Copernicus, which was mathematically achieved by reversing the direction of the last vector connecting the Earth to the Sun. In the published version of his masterwork, De revolutionibus orbium coelestium
De revolutionibus orbium coelestium
De revolutionibus orbium coelestium is the seminal work on the heliocentric theory of the Renaissance astronomer Nicolaus Copernicus...

, Copernicus also cites the theories of al-Battani
Al-Battani
Abū ʿAbd Allāh Muḥammad ibn Jābir ibn Sinān al-Raqqī al-Ḥarrānī al-Ṣābiʾ al-Battānī was a Muslim astronomer, astrologer, and mathematician...

, Arzachel
Arzachel
', Al-Zarqali, Ibn Zarqala , Latinized as Arzachel, was an instrument maker and one of the leading theoretical and practical astronomers of his time. Although his name is conventionally given as al-Zarqālī, it is probable that the correct form was al-Zarqālluh. He lived in Toledo in Castile,...

 and Averroes
Averroes
' , better known just as Ibn Rushd , and in European literature as Averroes , was a Muslim polymath; a master of Aristotelian philosophy, Islamic philosophy, Islamic theology, Maliki law and jurisprudence, logic, psychology, politics, Arabic music theory, and the sciences of medicine, astronomy,...

 as influences, while the works of Ibn al-Haytham and al-Biruni
Al-Biruni
Abū al-Rayḥān Muḥammad ibn Aḥmad al-BīrūnīArabic spelling. . The intermediate form Abū Rayḥān al-Bīrūnī is often used in academic literature...

 were also known in Europe at the time.

An area of active discussion in the Maragheh school, and later the Samarkand
Samarkand
Although a Persian-speaking region, it was not united politically with Iran most of the times between the disintegration of the Seleucid Empire and the Arab conquest . In the 6th century it was within the domain of the Turkic kingdom of the Göktürks.At the start of the 8th century Samarkand came...

 and Istanbul
Istanbul
Istanbul , historically known as Byzantium and Constantinople , is the largest city of Turkey. Istanbul metropolitan province had 13.26 million people living in it as of December, 2010, which is 18% of Turkey's population and the 3rd largest metropolitan area in Europe after London and...

 observatories, was the possibility of the Earth's rotation. Supporters of this theory included Nasīr al-Dīn al-Tūsī
Nasir al-Din al-Tusi
Khawaja Muḥammad ibn Muḥammad ibn Ḥasan Ṭūsī , better known as Naṣīr al-Dīn al-Ṭūsī , was a Persian polymath and prolific writer: an astronomer, biologist, chemist, mathematician, philosopher, physician, physicist, scientist, theologian and Marja Taqleed...

, Nizam al-Din al-Nisaburi (c. 1311), al-Sayyid al-Sharif al-Jurjani (1339–1413), Ali Qushji (d. 1474), and Abd al-Ali al-Birjandi
Al-Birjandi
Abd Ali ibn Muhammad ibn Husayn Birjandi was a prominent 16th century Persian astronomer, mathematician and physicist who lived in Birjand, Iran.- His works :...

 (d. 1525). Al-Tusi was the first to present empirical observational evidence of the Earth's rotation, using the location of comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...

s relevant to the Earth as evidence, which Qushji elaborated on with further empirical observations while rejecting Aristotelian natural philosophy
Natural philosophy
Natural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...

 altogether. Both of their arguments were similar to the arguments later used by Nicolaus Copernicus
Nicolaus Copernicus
Nicolaus Copernicus was a Renaissance astronomer and the first person to formulate a comprehensive heliocentric cosmology which displaced the Earth from the center of the universe....

 in 1543 to explain the Earth's rotation (see Astronomical physics and Earth's motion section below).

Experimental astrophysics and celestial mechanics


In the 9th century, the eldest Banū Mūsā
Banu Musa
The Banū Mūsā brothers , namely Abū Jaʿfar Muḥammad ibn Mūsā ibn Shākir , Abū al‐Qāsim Aḥmad ibn Mūsā ibn Shākir and Al-Ḥasan ibn Mūsā ibn Shākir , were three 9th-century Persian scholars of Baghdad who are known for their Book of Ingenious Devices on automata and mechanical devices...

 brother, Ja'far Muhammad ibn Mūsā ibn Shākir, made significant contributions to Islamic astrophysics
Islamic physics
Physics in medieval Islam is the development of physics in the medieval Islamic world in the history of physics. In the course of the expansion of the Islamic world, Muslim scholars encountered the science, mathematics, and medicine of antiquity through the works of Aristotle, Archimedes, Galen,...

 and celestial mechanics
Celestial mechanics
Celestial mechanics is the branch of astronomy that deals with the motions of celestial objects. The field applies principles of physics, historically classical mechanics, to astronomical objects such as stars and planets to produce ephemeris data. Orbital mechanics is a subfield which focuses on...

. He was the first to hypothesize that the heavenly bodies and celestial spheres
Celestial spheres
The celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus and others...

 are subject to the same laws of physics
Physical law
A physical law or scientific law is "a theoretical principle deduced from particular facts, applicable to a defined group or class of phenomena, and expressible by the statement that a particular phenomenon always occurs if certain conditions be present." Physical laws are typically conclusions...

 as Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

, unlike the ancients who believed that the celestial spheres followed their own set of physical laws different from that of Earth. In his Astral Motion and The Force of Attraction, Muhammad ibn Musa also proposed that there is a force
Force
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...

 of attraction
Gravitation
Gravitation, or gravity, is a natural phenomenon by which physical bodies attract with a force proportional to their mass. Gravitation is most familiar as the agent that gives weight to objects with mass and causes them to fall to the ground when dropped...

 between heavenly bodies
Astronomical object
Astronomical objects or celestial objects are naturally occurring physical entities, associations or structures that current science has demonstrated to exist in the observable universe. The term astronomical object is sometimes used interchangeably with astronomical body...

, foreshadowing Newton's law of universal gravitation
Newton's law of universal gravitation
Newton's law of universal gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them...

.

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
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

 and the earliest attempt at applying the experimental method
Scientific method
Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...

 to astronomy and astrophysics
Astrophysics
Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior...

. He disproved the universally held opinion that the moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 reflects sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...

 like a mirror
Mirror
A mirror is an object that reflects light or sound in a way that preserves much of its original quality prior to its contact with the mirror. Some mirrors also filter out some wavelengths, while preserving other wavelengths in the reflection...

 and correctly concluded that it "emits light from those portions of its surface which the sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

's light strikes." In order to prove that "light is emitted from every point of the moon's illuminated surface," he built an "ingenious experiment
Experiment
An experiment is a methodical procedure carried out with the goal of verifying, falsifying, or establishing the validity of a hypothesis. Experiments vary greatly in their goal and scale, but always rely on repeatable procedure and logical analysis of the results...

al 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
Radiance
Radiance and spectral radiance are radiometric measures that describe the amount of radiation such as light or radiant heat that passes through or is emitted from a particular area, and falls within a given solid angle in a specified direction. They are used to characterize both emission from...

 of the light-spot formed by the projection of the moonlight
Moonlight
Moonlight is the light that reaches Earth from the Moon. This light does not originate from the Moon, but from sunlight. The Moon does not, however, reflect sunlight like a mirror, but it reflects light from those portions of its surface which the Sun's light strikes. See diffuse reflection.In...

 through two small aperture
Aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are,...

s onto a screen diminishes constantly as one of the apertures is gradually blocked up."

Ibn al-Haytham, in his Book of Optics
Book of Optics
The Book of Optics ; ; Latin: De Aspectibus or Opticae Thesaurus: Alhazeni Arabis; Italian: Deli Aspecti) is a seven-volume treatise on optics and other fields of study composed by the medieval Muslim scholar Alhazen .-See also:* Science in medieval Islam...

 (1021), was also the first to discover that the celestial spheres
Celestial spheres
The celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus and others...

 do not consist of solid
Solid
Solid is one of the three classical states of matter . It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a...

 matter, and he also discovered that the heavens are less dense than the air. These views were later repeated by Witelo
Witelo
Witelo was a friar, theologian and scientist: a physicist, natural philosopher, mathematician. He is an important figure in the history of philosophy in Poland...

 and had a significant influence on the Copernican
Copernican heliocentrism
Copernican heliocentrism is the name given to the astronomical model developed by Nicolaus Copernicus and published in 1543. It positioned the Sun near the center of the Universe, motionless, with Earth and the other planets rotating around it in circular paths modified by epicycles and at uniform...

 and Tychonic system
Tychonic system
The Tychonic system was a model of the solar system published by Tycho Brahe in the late 16th century which combined what he saw as the mathematical benefits of the Copernican system with the philosophical and "physical" benefits of the Ptolemaic system...

s of astronomy.

In the 12th century, Fakhr al-Din al-Razi
Fakhr al-Din al-Razi
Abu Abdullah Muhammad ibn Umar ibn al-Husayn al-Taymi al-Bakri al-Tabaristani Fakhr al-Din al-Razi , most commonly known as Fakhruddin Razi was a well-known Persian Sunni Muslim theologian and philosopher....

 participated in the debate among Islamic scholars over whether the celestial spheres
Celestial spheres
The celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus and others...

 or orbits (falak) are "to be considered as real, concrete physical bodies" or "merely the abstract circles in the heavens traced out year in and year out by the various stars and planets." He points out that many astronomers prefer to see them as solid spheres "on which the stars turn," while others, such as the Islamic scholar Dahhak, view the celestial sphere as "not a body but merely the abstract orbit traced by the stars." Al-Razi himself remains "undecided as to which celestial models
Celestial mechanics
Celestial mechanics is the branch of astronomy that deals with the motions of celestial objects. The field applies principles of physics, historically classical mechanics, to astronomical objects such as stars and planets to produce ephemeris data. Orbital mechanics is a subfield which focuses on...

, concrete or abstract, most conform with external reality," and notes that "there is no way to ascertain the characteristics of the heavens," whether by "observable" evidence or by authority (al-khabar) of "divine revelation
Qur'an
The Quran , also transliterated Qur'an, Koran, Alcoran, Qur’ān, Coran, Kuran, and al-Qur’ān, is the central religious text of Islam, which Muslims consider the verbatim word of God . It is regarded widely as the finest piece of literature in the Arabic language...

 or prophetic traditions
Sunnah
The word literally means a clear, well trodden, busy and plain surfaced road. In the discussion of the sources of religion, Sunnah denotes the practice of Prophet Muhammad that he taught and practically instituted as a teacher of the sharī‘ah and the best exemplar...

." He concludes that "astronomical models, whatever their utility or lack thereof for ordering the heavens, are not founded on sound rational proofs, and so no intellectual commitment can be made to them insofar as description and explanation of celestial realities are concerned."

The theologian Adud al-Din al-Iji (1281–1355), under the influence of the Ash'ari
Ash'ari
The Ashʿari theology is a school of early Muslim speculative theology founded by the theologian Abu al-Hasan al-Ash'ari...

 doctrine of occasionalism
Occasionalism
Occasionalism is a philosophical theory about causation which says that created substances cannot be efficient causes of events. Instead, all events are taken to be caused directly by God...

, which maintained that all physical effects were caused directly by God's will rather than by natural causes, rejected the Aristotelian principle
Aristotelian physics
Aristotelian Physics the natural sciences, are described in the works of the Greek philosopher Aristotle . In the Physics, Aristotle established general principles of change that govern all natural bodies; both living and inanimate, celestial and terrestrial—including all motion, change in respect...

 of an innate principle of circular motion in the heavenly bodies, and maintained that the celestial spheres were "imaginary things" and "more tenuous than a spider's web".

Astronomical physics and Earth's motion


The work of Ali Qushji (d. 1474), who worked at Samarkand
Samarkand
Although a Persian-speaking region, it was not united politically with Iran most of the times between the disintegration of the Seleucid Empire and the Arab conquest . In the 6th century it was within the domain of the Turkic kingdom of the Göktürks.At the start of the 8th century Samarkand came...

 and then Istanbul
Istanbul
Istanbul , historically known as Byzantium and Constantinople , is the largest city of Turkey. Istanbul metropolitan province had 13.26 million people living in it as of December, 2010, which is 18% of Turkey's population and the 3rd largest metropolitan area in Europe after London and...

, is seen as a late example of innovation in Islamic theoretical astronomy and it is believed he may have possibly had some influence on Nicolaus Copernicus
Nicolaus Copernicus
Nicolaus Copernicus was a Renaissance astronomer and the first person to formulate a comprehensive heliocentric cosmology which displaced the Earth from the center of the universe....

 due to similar arguments concerning the Earth's rotation. Before Qushji, the only astronomer to present empirical evidence
Empirical research
Empirical research is a way of gaining knowledge by means of direct and indirect observation or experience. Empirical evidence can be analyzed quantitatively or qualitatively...

 for the Earth's rotation was Nasīr al-Dīn al-Tūsī
Nasir al-Din al-Tusi
Khawaja Muḥammad ibn Muḥammad ibn Ḥasan Ṭūsī , better known as Naṣīr al-Dīn al-Ṭūsī , was a Persian polymath and prolific writer: an astronomer, biologist, chemist, mathematician, philosopher, physician, physicist, scientist, theologian and Marja Taqleed...

 (d. 1274), who used the phenomena of comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...

s to refute Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

's claim that a stationary Earth can be determined through observation. Al-Tusi, however, eventually accepted that the Earth was stationary on the basis of Aristotelian cosmology
On the Heavens
On the Heavens is Aristotle's chief cosmological treatise: it contains his astronomical theory and his ideas on the concrete workings of the terrestrial world...

 and natural philosophy
Natural philosophy
Natural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...

. By the 15th century, the influence of Aristotelian physics
Aristotelian physics
Aristotelian Physics the natural sciences, are described in the works of the Greek philosopher Aristotle . In the Physics, Aristotle established general principles of change that govern all natural bodies; both living and inanimate, celestial and terrestrial—including all motion, change in respect...

 and natural philosophy was declining due to religious opposition from Islamic theologians
Islamic theology
Islamic theology is a branch of Islamic studies regarding the beliefs associated with the Islamic faith. Any religious belief system, or creed, can be considered an example of aqidah. However, this term has taken a significant technical usage in Islamic history and theology, denoting those...

 such as Al-Ghazali
Al-Ghazali
Abu Hāmed Mohammad ibn Mohammad al-Ghazzālī , known as Algazel to the western medieval world, born and died in Tus, in the Khorasan province of Persia was a Persian Muslim theologian, jurist, philosopher, and mystic....

 who opposed to the interference of Aristotelianism
Aristotelianism
Aristotelianism is a tradition of philosophy that takes its defining inspiration from the work of Aristotle. The works of Aristotle were initially defended by the members of the Peripatetic school, and, later on, by the Neoplatonists, who produced many commentaries on Aristotle's writings...

 in astronomy, opening up possibilities for an astronomy unrestrained by philosophy. Under this influence, Qushji, in his Concerning the Supposed Dependence of Astronomy upon Philosophy, rejected Aristotelian physics and completely separated natural philosophy from astronomy, allowing astronomy to become a purely empirical
Empirical
The word empirical denotes information gained by means of observation or experimentation. Empirical data are data produced by an experiment or observation....

 and mathematical science. This allowed him to explore alternatives to the Aristotelian notion of a stationary Earth, as he explored the idea of a moving Earth. He also observed comets and elaborated on al-Tusi's argument. He took it a step further and concluded, on the basis of empirical evidence rather than speculative philosophy, that the moving Earth theory is just as likely to be true as the stationary Earth theory and that it is not possible to empirically deduce which theory is true. His work was an important step away from Aristotelian physics and towards an independent astronomical physics
Astrophysics
Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior...

.

Despite the similarity in their discussions regarding the Earth's motion, there is uncertainty over whether Qushji had any influence on Copernicus. However, it is likely that they both may have arrived at similar conclusions due to using the earlier work of al-Tusi as a basis. This is more of a possibility considering "the remarkable coincidence between a passage in De revolutionibus (I.8) and one in Ṭūsī’s Tadhkira (II.1[6]) in which Copernicus follows Ṭūsī’s objection to Ptolemy’s “proofs” of the Earth’s immobility." This can be considered as evidence that not only was Copernicus influenced by the mathematical models of Islamic astronomers, but may have also been influenced by the astronomical physics they began developing and their views on the Earth's motion.

In the 16th century, the debate on the Earth's motion was continued by al-Birjandi
Al-Birjandi
Abd Ali ibn Muhammad ibn Husayn Birjandi was a prominent 16th century Persian astronomer, mathematician and physicist who lived in Birjand, Iran.- His works :...

 (d. 1528), who in his analysis of what might occur if the Earth were moving, develops a hypothesis similar to Galileo Galilei
Galileo Galilei
Galileo Galilei , was an Italian physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations and support for Copernicanism...

's notion of "circular inertia
Inertia
Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. It is proportional to an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to...

", which he described in the following observational test (as a response to one of Qutb al-Din al-Shirazi
Qutb al-Din al-Shirazi
Qotb al-Din Shirazi or Qutb al-Din al-Shirazi was a 13th century Persian Muslim polymath and Persian poet who made contributions astronomy, mathematics, medicine, physics, music theory, philosophy and Sufism.- Biography :...

's arguments):

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