Islamic cosmology is the cosmology of Islamic
societies. It is mainly derived from the Qur'an,
Hadith, Sunnah, and current Islamic as well
as other pre-Islamic sources. The Qur'an itself
mentions seven heavens.
== Metaphysical principles ==
=== 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,
angels, Paradise, Hell, seven heavens, and
Al-Arsh (the Divine Throne)[1]; 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."
== Sufi cosmology ==
Sufi cosmology (Arabic: الكوزمولوجية
الصوفية‎) is a general term for cosmological
doctrines associated with the mysticism of
Sufism. These may differ from place to place,
order to order and time to time, but overall
show the influence of several different cosmographies:
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 like Avicenna and Ibn Arabi.
The Hermetic-Ptolemaic spherical geocentric
world.
The Ishraqi visionary universe as expounded
by Suhrawardi Maqtul.
== Quranic interpretations ==
There are several verses in the Qur'an (610-632)
which some medieval and modern writers have
interpreted as foreshadowing modern cosmological
theories. An early example of this can be
seen in the work of the Islamic theologian
Fakhr al-Din al-Razi (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 within the universe, and explores
"the notion of the existence of a multiverse
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 worlds within this single universe
or cosmos, 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 theory of atomism.
== Cosmology in the medieval Islamic world
==
Cosmology was studied extensively in the Muslim
world during what is known as the Islamic
Golden Age 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. However, it also corrected Ptolemy's
Almagest based on findings of earlier Iranian
astronomers. Al-Farghani gave revised values
for the obliquity of the ecliptic, the precessional
movement of the apogees of the sun and the
moon, and the circumference of the earth.
The books were widely circulated through the
Muslim world, and even translated into Latin.
=== Cosmography ===
ʿAjā'ib al-makhlūqāt wa gharā'ib al-mawjūdāt
(Arabic: عجائب المخلوقات و
غرائب الموجودات‎, meaning
Marvels of creatures and Strange things existing)
is an important work of cosmography by Zakariya
ibn Muhammad ibn Mahmud Abu Yahya al-Qazwini
who was born in Qazwin year 600 (AH (1203
AD).
=== Temporal finitism ===
In contrast to ancient Greek philosophers
who believed that the universe had an infinite
past with no beginning, medieval philosophers
and theologians developed the concept of the
universe having a finite past with a beginning
(see Temporal finitism). The Christian philosopher,
John Philoponus, 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,
Al-Kindi (Alkindus); the Jewish philosopher,
Saadia Gaon (Saadia ben Joseph); and the Muslim
theologian, Al-Ghazali (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 in his thesis of the first antinomy
concerning time.
=== Galaxy observation ===
The Arabian astronomer Alhazen (965–1037)
made the first attempt at observing and measuring
the Milky Way's parallax, and he thus "determined
that because the Milky Way had no parallax,
it was very remote from the earth and did
not belong to the atmosphere." The Persian
astronomer Abū Rayhān al-Bīrūnī (973–1048)
proposed the Milky Way galaxy to be "a collection
of countless fragments of the nature of nebulous
stars." The Andalusian astronomer Ibn Bajjah
("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 from
sublunary material, citing his observation
of the conjunction of Jupiter and Mars on
500 AH (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, describing it as a "small
cloud". Al-Sufi also identified the Large
Magellanic Cloud, which is visible from Yemen,
though not from Isfahan; it was not seen by
Europeans until Magellan'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 in 964.
=== Possible worlds ===
Al-Ghazali, in The Incoherence of the Philosophers,
defends the Ash'ari doctrine of a created
universe that is temporally finite, against
the Aristotelian doctrine of an eternal universe.
In doing so, he proposed the modal theory
of possible worlds, arguing that their actual
world is the best of all possible worlds from
among all the alternate timelines and world
histories that God could have possibly created.
His theory parallels that of Duns Scotus 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's Metaphysics.
=== Multiversal cosmology ===
Fakhr al-Din al-Razi (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 within
the universe and "explores the notion of the
existence of a multiverse 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
worlds within this single universe or cosmos,
or to many other universes or a multiverse
beyond this known universe." In volume 4 of
the Matalib, Al-Razi states:
It is established by evidence that there exists
beyond the world a void without a terminal
limit (khala' la nihayata laha), and it is
established as well by evidence that God Most
High has power over all contingent beings
(al-mumkinat). Therefore He the Most High
has the power (qadir) to create a thousand
thousand worlds (alfa alfi 'awalim) beyond
this world such that each one of those worlds
be bigger and more massive than this world
as well as having the like of what this world
has of the throne (al-arsh), the chair (al-kursiyy),
the heavens (al-samawat) and the earth (al-ard),
and the sun (al-shams) and the moon (al-qamar).
The arguments of the philosophers (dala'il
al-falasifah) for establishing that the world
is one are weak, flimsy arguments founded
upon feeble premises.
Al-Razi rejected the Aristotelian 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, as advocated by the
Ash'ari school of Islamic theology, which
entails the existence of vacant space in which
the atoms move, combine and separate. He discussed
in greater detail the void, the empty space
between stars and constellations in the Universe,
in volume 5 of the Matalib. He argued that
there exists an infinite outer space beyond
the known world, and that God has the power
to fill the vacuum 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,
Ibn al-Haytham, Avicenna, Biruni and Averroes.
Their reasons for refuting astrology were
often due to both scientific (the methods
used by astrologers being conjectural rather
than empirical) and religious (conflicts with
orthodox Islamic scholars) reasons.Ibn Qayyim
Al-Jawziyya (1292–1350), in his Miftah Dar
al-SaCadah, used empirical arguments in astronomy
in order to refute the practice of astrology
and divination. He recognized that the stars
are much larger than the planets, and thus
argued:
"And if you astrologers answer that it is
precisely because of this distance and smallness
that their influences are negligible, then
why is it that you claim a great influence
for the smallest heavenly body, Mercury? Why
is it that you have given an influence to
al-Ra's and al-Dhanab, which are two imaginary
points [ascending and descending nodes]?"
Al-Jawziyya also recognized the Milky Way
galaxy as "a myriad of tiny stars packed together
in the sphere of the fixed stars" and thus
argued that "it is certainly impossible to
have knowledge of their influences."
=== Early heliocentric models ===
The Hellenistic Greek astronomer Seleucus
of Seleucia, who advocated a heliocentric
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 Muhammad ibn Zakariya al-Razi
(865-925).In the late ninth century, Ja'far
ibn Muhammad Abu Ma'shar al-Balkhi (Albumasar)
developed a planetary model which some have
interpreted as a heliocentric model. This
is due to his orbital revolutions of the planets
being given as heliocentric revolutions rather
than geocentric revolutions, and the only
known planetary theory in which this occurs
is in the heliocentric theory. His work on
planetary theory has not survived, but his
astronomical data was later recorded by al-Hashimi,
Abū Rayhān al-Bīrūnī and al-Sijzi.In
the early eleventh century, al-Biruni had
met several Indian scholars who believed in
a heliocentric system. In his Indica, he discusses
the theories on the Earth's rotation supported
by Brahmagupta and other Indian astronomers,
while in his Canon Masudicus, al-Biruni writes
that Aryabhata's followers assigned the first
movement from east to west to the Earth and
a second movement from west to east to the
fixed stars. Al-Biruni also wrote that al-Sijzi
also believed the Earth was moving and invented
an astrolabe called the "Zuraqi" based on
this idea:
"I have seen the astrolabe called Zuraqi invented
by Abu Sa'id Sijzi. I liked it very much and
praised him a great deal, as it is based on
the idea entertained by some to the effect
that the motion we see is due to the Earth's
movement and not to that of the sky. By my
life, it is a problem difficult of solution
and refutation. [...] For it is the same whether
you take it that the Earth is in motion or
the sky. For, in both cases, it does not affect
the Astronomical Science. It is just for the
physicist to see if it is possible to refute
it."
In his Indica, al-Biruni briefly refers to
his work on the refutation of heliocentrism,
the Key of Astronomy, which is now lost:
"The most prominent of both modern and ancient
astronomers have deeply studied the question
of the moving earth, and tried to refute it.
We, too, have composed a book on the subject
called Miftah 'ilm al-hai'ah (Key of Astronomy),
in which we think we have surpassed our predecessors,
if not in the words, at all events in the
matter."
=== 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) from philosophical
cosmology (as typified by Aristotle). Muslim
scholars developed a program of seeking a
physically real configuration (hay'a) of the
universe, that would be consistent with both
mathematical and physical principles. Within
the context of this hay'a tradition, Muslim
astronomers began questioning technical details
of the Ptolemaic system of astronomy.Some
Muslim astronomers, however, most notably
Abū Rayhān al-Bīrūnī and Nasīr al-Dīn
al-Tūsī, discussed whether the Earth moved
and considered how this might be consistent
with astronomical computations and physical
systems. Several other Muslim astronomers,
most notably those following the Maragha school
of astronomy, developed non-Ptolemaic planetary
models within a geocentric context that were
later adapted by the Copernican model in a
heliocentric context.
Between 1025 and 1028, Ibn al-Haytham (Latinized
as Alhazen), began the hay'a tradition of
Islamic astronomy with his Al-Shuku ala Batlamyus
(Doubts on Ptolemy). While maintaining the
physical reality of the geocentric model,
he was the first to criticize Ptolemy's astronomical
system, which he criticized on empirical,
observational and experimental grounds, 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."In
1038, Ibn al-Haytham described the first non-Ptolemaic
configuration in The Model of the Motions.
His reform was not concerned with cosmology,
as he developed a systematic study of celestial
kinematics that was completely geometric.
This in turn led to innovative developments
in infinitesimal geometry. His reformed model
was the first to reject the equant and eccentrics,
separate natural philosophy from astronomy,
free celestial kinematics from cosmology,
and reduce physical entities to geometrical
entities. The model also propounded the Earth's
rotation about its axis, and the centres of
motion were geometrical points without any
physical significance, like Johannes Kepler's
model centuries later. Ibn al-Haytham also
describes an early version of Occam's razor,
where he employs only minimal hypotheses regarding
the properties that characterize astronomical
motions, as he attempts to eliminate from
his planetary model the cosmological hypotheses
that cannot be observed from Earth.In 1030,
Abū al-Rayhān al-Bīrūnī discussed the
Indian planetary theories of Aryabhata, Brahmagupta
and Varahamihira in his Ta'rikh al-Hind (Latinized
as Indica). Biruni stated that Brahmagupta
and others consider that the earth rotates
on its axis and Biruni noted that this does
not create any mathematical problems. Abu
Said al-Sijzi, a contemporary of al-Biruni,
suggested the possible heliocentric movement
of the Earth around the Sun, which al-Biruni
did not reject. Al-Biruni agreed with the
Earth's rotation about its own axis, and while
he was initially neutral regarding the heliocentric
and geocentric models, he considered heliocentrism
to be a philosophical problem. He remarked
that if the Earth rotates on its axis and
moves around the Sun, it would remain consistent
with his astronomical parameters:
"Rotation of the earth would in no way invalidate
astronomical calculations, for all the astronomical
data are as explicable in terms of the one
theory as of the other. The problem is thus
difficult of solution."
=== Andalusian Revolt ===
In the 11th-12th centuries, astronomers in
al-Andalus took up the challenge earlier posed
by Ibn al-Haytham, namely to develop an alternate
non-Ptolemaic configuration that evaded the
errors found in the Ptolemaic model. Like
Ibn al-Haytham's critique, the anonymous Andalusian
work, al-Istidrak ala Batlamyus (Recapitulation
regarding Ptolemy), included a list of objections
to Ptolemic astronomy. This marked the beginning
of the Andalusian school's revolt against
Ptolemaic astronomy, otherwise known as the
"Andalusian Revolt".In the 12th century, Averroes
rejected the eccentric deferents introduced
by Ptolemy. He rejected the Ptolemaic model
and instead argued for a strictly concentric
model of the universe. He wrote the following
criticism on the Ptolemaic model of planetary
motion:
"To assert the existence of an eccentric sphere
or an epicyclic sphere is contrary to nature.
[...] The astronomy of our time offers no
truth, but only agrees with the calculations
and not with what exists."
Averroes' contemporary, Maimonides, wrote
the following on the planetary model proposed
by Ibn Bajjah (Avempace):
"I have heard that Abu Bakr [Ibn Bajja] discovered
a system in which no epicycles occur, but
eccentric spheres are not excluded by him.
I have not heard it from his pupils; and even
if it be correct that he discovered such a
system, he has not gained much by it, for
eccentricity is likewise contrary to the principles
laid down by Aristotle.... I have explained
to you that these difficulties do not concern
the astronomer, for he does not profess to
tell us the existing properties of the spheres,
but to suggest, whether correctly or not,
a theory in which the motion of the stars
and planets is uniform and circular, and in
agreement with observation."
Ibn Bajjah also proposed the Milky Way galaxy
to be made up of many stars but that it appears
to be a continuous image due to the effect
of refraction in the Earth's atmosphere. Later
in the 12th century, his successors Ibn Tufail
and Nur Ed-Din Al Betrugi (Alpetragius) were
the first to propose planetary models without
any equant, epicycles or eccentrics. Their
configurations, however, were not accepted
due to the numerical predictions of the planetary
positions in their models being less accurate
than that of the Ptolemaic model, mainly because
they followed Aristotle's notion of perfectly
uniform circular motion.
=== Maragha Revolution ===
The "Maragha Revolution" refers to the Maragheh
school's revolution against Ptolemaic astronomy.
The "Maragha school" was an astronomical tradition
beginning in the Maragheh observatory and
continuing with astronomers from Damascus
and Samarkand. Like their Andalusian predecessors,
the Maragha astronomers attempted to solve
the equant problem and produce alternative
configurations to the Ptolemaic model. They
were more successful than their Andalusian
predecessors in producing non-Ptolemaic configurations
which eliminated the equant and eccentrics,
were more accurate than the Ptolemaic model
in numerically predicting planetary positions,
and were in better agreement with empirical
observations. The most important of the Maragha
astronomers included Mo'ayyeduddin Urdi (d.
1266), Nasīr al-Dīn al-Tūsī (1201–1274),
Najm al-Dīn al-Qazwīnī al-Kātibī (d.
1277), Qutb al-Din al-Shirazi (1236–1311),
Sadr al-Sharia al-Bukhari (c. 1347), Ibn al-Shatir
(1304–1375), Ali Qushji (c. 1474), al-Birjandi
(d. 1525) and Shams al-Din al-Khafri (d. 1550).Some
have described their achievements in the 13th
and 14th centuries as a "Maragha Revolution",
"Maragha School Revolution", or "Scientific
Revolution before the Renaissance". An important
aspect of this revolution included the realization
that astronomy should aim to describe the
behavior of physical bodies in mathematical
language, and should not remain a mathematical
hypothesis, which would only save the phenomena.
The Maragha astronomers also realized that
the Aristotelian view of motion in the universe
being only circular or linear was not true,
as the Tusi-couple showed that linear motion
could also be produced by applying circular
motions only.Unlike the ancient Greek and
Hellenistic astronomers who were not concerned
with the coherence between the mathematical
and physical principles of a planetary theory,
Islamic astronomers insisted on the need to
match the mathematics with the real world
surrounding them, which gradually evolved
from a reality based on Aristotelian physics
to one based on an empirical and mathematical
physics after the work of Ibn al-Shatir. The
Maragha Revolution was thus characterized
by a shift away from the philosophical foundations
of Aristotelian cosmology and Ptolemaic astronomy
and towards a greater emphasis on the empirical
observation and mathematization of astronomy
and of nature in general, as exemplified in
the works of Ibn al-Shatir, 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
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.Mo'ayyeduddin
Urdi (d. 1266) was the first of the Maragheh
astronomers to develop a non-Ptolemaic model,
and he proposed a new theorem, the "Urdi lemma".
Nasīr al-Dīn al-Tūsī (1201–1274) resolved
significant problems in the Ptolemaic system
by developing the Tusi-couple as an alternative
to the physically problematic equant introduced
by Ptolemy. Tusi's student Qutb al-Din al-Shirazi
(1236–1311), in his The Limit of Accomplishment
concerning Knowledge of the Heavens, discussed
the possibility of heliocentrism. 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 (1304–1375) of Damascus, in
A Final Inquiry Concerning the Rectification
of Planetary Theory, incorporated the Urdi
lemma, and eliminated the need for an equant
by introducing an extra epicycle (the Tusi-couple),
departing from the Ptolemaic system in a way
that was mathematically identical to what
Nicolaus Copernicus did in the 16th century.
Unlike previous astronomers before him, Ibn
al-Shatir was not concerned with adhering
to the theoretical principles of natural philosophy
or Aristotelian cosmology, but rather to produce
a model that was more consistent with empirical
observations. For example, it was Ibn al-Shatir's
concern for observational accuracy which led
him to eliminate the epicycle in the Ptolemaic
solar model and all the eccentrics, epicycles
and equant in the Ptolemaic lunar model. His
model was thus in better agreement with empirical
observations than any previous model, and
was also the first that permitted empirical
testing. 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 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, Copernicus
also cites the theories of al-Battani and
Averroes as influences.An area of active discussion
in the Maragheh school, and later the Samarkand
and Istanbul observatories, was the possibility
of the Earth's rotation. Supporters of this
theory included Nasīr al-Dīn al-Tūsī,
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 (d.
1525). Al-Tusi was the first to present empirical
observational evidence of the Earth's rotation,
using the location of comets relevant to the
Earth as evidence, which Qushji elaborated
on with further empirical observations while
rejecting Aristotelian natural philosophy
altogether. Both of their arguments were similar
to the arguments later used by Nicolaus Copernicus
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
brother, Ja'far Muhammad ibn Mūsā ibn Shākir,
made significant contributions to Islamic
astrophysics and celestial mechanics. He was
the first to hypothesize that the heavenly
bodies and celestial spheres are subject to
the same laws of physics as Earth, 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 of attraction between heavenly
bodies, foreshadowing Newton's law of universal
gravitation.In the early 11th century, Ibn
al-Haytham (Alhazen) wrote the Maqala fi daw
al-qamar (On the Light of the Moon) some time
before 1021. This was the first attempt successful
at combining mathematical astronomy with physics
and the earliest attempt at applying the experimental
method to astronomy and astrophysics. He disproved
the universally held opinion that the moon
reflects sunlight like a mirror and correctly
concluded that it "emits light from those
portions of its surface which the sun's light
strikes." In order to prove that "light is
emitted from every point of the moon's illuminated
surface," he built an "ingenious experimental
device." Ibn al-Haytham had "formulated a
clear conception of the relationship between
an ideal mathematical model and the complex
of observable phenomena; in particular, he
was the first to make a systematic use of
the method of varying the experimental conditions
in a constant and uniform manner, in an experiment
showing that the intensity of the light-spot
formed by the projection of the moonlight
through two small apertures onto a screen
diminishes constantly as one of the apertures
is gradually blocked up."Ibn al-Haytham, in
his Book of Optics (1021), was also the first
to discover that the celestial spheres do
not consist of solid matter, and he also discovered
that the heavens are less dense than the air.
These views were later repeated by Witelo
and had a significant influence on the Copernican
and Tychonic systems of astronomy.In the 12th
century, Fakhr al-Din al-Razi participated
in the debate among Islamic scholars over
whether the celestial spheres 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, 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 or prophetic traditions."
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 doctrine of occasionalism, which maintained
that all physical effects were caused directly
by God's will rather than by natural causes,
rejected the Aristotelian principle 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". His views were
challenged by al-Jurjani (1339–1413), who
argued that even if the celestial spheres
"do not have an external reality, yet they
are things that are correctly imagined and
correspond to what [exists] in actuality".
=== Astronomical physics and Earth's motion
===
The work of Ali Qushji (d. 1474), who worked
at Samarkand and then Istanbul, 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
due to similar arguments concerning the Earth's
rotation. Before Qushji, the only astronomer
to present empirical evidence for the Earth's
rotation was Nasīr al-Dīn al-Tūsī (d.
1274), who used the phenomena of comets to
refute Ptolemy'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 and natural philosophy. By the 15th
century, the influence of Aristotelian physics
and natural philosophy was declining due to
religious opposition from Islamic theologians
such as Al-Ghazali who opposed to the interference
of Aristotelianism 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 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.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 (d. 1528), who
in his analysis of what might occur if the
Earth were moving, develops a hypothesis similar
to Galileo Galilei's notion of "circular inertia",
which he described in the following observational
test (as a response to one of Qutb al-Din
al-Shirazi's arguments):
"The small or large rock will fall to the
Earth along the path of a line that is perpendicular
to the plane (sath) of the horizon; this is
witnessed by experience (tajriba). And this
perpendicular is away from the tangent point
of the Earth’s sphere and the plane of the
perceived (hissi) horizon. This point moves
with the motion of the Earth and thus there
will be no difference in place of fall of
the two rocks."
== 
See also ==
Astronomy in medieval Islam
Bahá'í cosmology
Buddhist cosmology
Christian cosmology
Hindu cosmology
Jain cosmology
Religious cosmology
Arcs of Descent and Ascent
== 
Notes ==
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== External links ==
The Quran and Cosmology
Dr Israr Ahmed [2]
