Ali Kusçu
Encyclopedia
Ala al-Dīn Ali ibn Muhammed (1403 – 16 December 1474), known as Ali Qushji (Ottoman Turkish
/Persian language
: علی قوشچی, kuşçu - falconer
in Turkish; Latin
: Ali Kushgii), was a Turkic
or Persian astronomer
, mathematician
and physicist
originally from Samarkand
, who settled in the Ottoman Empire
some time before 1472. As a disciple of Ulugh Beg
, he is best known for the development of astronomical physics
independent from natural philosophy
, and for providing empirical evidence for the Earth's rotation in his treatise, Concerning the Supposed Dependence of Astronomy upon Philosophy. In addition to his contributions to Ulugh Beg
's famous work Zij-i-Sultani
and to the founding of Sahn-ı Seman University, one of the first madrasahs in the Ottoman Empire, Ali Qushji was also the author of several scientific works and textbooks on astronomy.
, in present-day Uzbekistan
. His full name at birth was Ala al-Dīn Ali ibn Muhammed al-Qushji. The last name Qushji derived from the Turkish term kuşçu - the falconer - due to the fact that Ali's father Muhammad was the royal falconer
of Ulugh Beg
.
He attended the courses of Qazi zadeh Rumi, Ghiyāth al-Dīn Jamshīd Kāshānī
and Muin al-Dīn Kashi. He moved to Kerman, Iran (Persia) and there he conducted some researches on the storms of Oman sea. He completed Hall-e Eshkal-i Ghammar (Explanations of the Periods of the Moon) and Sharh-e Tajrid in Kirman. He moved to Herat and taught Molla Cami about astronomy (1423). After professing in Herat for a while he went back to Samarkand and herald his works about moon to Ulugh Beg. Ulugh Beg was fascinated with the works and read the entire work while standing up. Ulugh Beg assigned him to Ulugh Beg Observatory
which was called "Samarkand Observatory" at that time. He worked there till Ulugh Beg was assassinated.
After Ulugh Beg's death, Ali Qushji went to Herat, Tashkent
and finally Tabriz
, where around 1470, the Ak Koyunlu
ruler Uzun Hasan sent him as a delegate to the Ottoman Sultan Mehmed II
. At that time Husayn Bayqarah
had come to reign in Herat but Qushji preferred Constantinople rather than Herat because of Sultan Mehmed's attitude toward scientists and intellectuals.
), his grandson Ghutb al-Dīn Muhammed had a son Mirim Chalabi who would be a great mathematician and astronomer in the future. Ali Qushji composed "risalah dar hay’at" in Persian
for Mehmed II
at Constantinople in 1470. Also he wrote "Sharh e resalye Fathiyeh", "resalye Mohammadiye" in Constantinople, which are in Arabic
on the topic of mathematics. Qushji's work made a great impact on the scientific community. The work has thousands of copies in handwriting libraries all around the world.
He then finished "Sharh e tejrid" on Nasir al-Din al-Tusi
's "Tejrid al-kalam". That work is called "Sharh e Jadid" in scientific community. It is considered as the most important philosophical work on metaphysics, physics, optics and mathematics done within Islamic civilization.
's planetary model and presented an alternative planetary model for Mercury
. He was also one of the astronomers that were part of Ulugh Beg
's team of researchers working at the Samarqand observatory
and contributed towards the Zij-i-Sultani
compiled there. In addition to his contributions to Zij, Ali Qushji wrote nine works in astronomy, two of them in Persian
and seven in Arabic
. A Latin
translation of two of Qushji's works, the Tract on Arithmetic and Tract on Astronomy, was published by John Greaves
in 1650.
who opposed the interference of Aristotelianism
in astronomy, Qushji rejected Aristotelian physics
and completely separated natural philosophy
from Islamic 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 instead. Though Savage-Smith asserts that no Islamic astronomers proposed a heliocentric universe. He found empirical evidence
for the Earth's rotation through his observation on comet
s 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.
His predecessor al-Tusi had previously realized that "the monoformity of falling bodies, and the uniformity of celestial motions," both moved “in a single way,” though he still relied on Aristotelian physics to provide "certain principles that only the natural philosophers could provide the astronomer." Qushji took this concept further and proposed that "the astronomer had no need for Aristotelian physics and in fact should establish his own physical principles independently of the natural philosophers." Alongside his rejection of Aristotle's concept of a stationary Earth, Qushji suggested that there was no need for astronomers to follow the Aristotelian notion of the heavenly bodies moving in uniform circular motion
.
Qushji's work was an important step away from Aristotelian physics and towards an independent astronomical physics
. This is considered to be a "conceptual revolution" that had no precedent in European astronomy prior to the Copernican Revolution
in the 16th century. Qushji's view on the Earth's motion was similar to the later views of Nicolaus Copernicus
on this issue, though it is uncertain whether the former had any influence on the latter. However, it is likely that they both may have arrived at similar conclusions due to using the earlier work of Nasir al-Din 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."
Ottoman Turkish language
The Ottoman Turkish language or Ottoman language is the variety of the Turkish language that was used for administrative and literary purposes in the Ottoman Empire. It borrows extensively from Arabic and Persian, and was written in a variant of the Perso-Arabic script...
/Persian language
Persian language
Persian is an Iranian language within the Indo-Iranian branch of the Indo-European languages. It is primarily spoken in Iran, Afghanistan, Tajikistan and countries which historically came under Persian influence...
: علی قوشچی, kuşçu - falconer
Falconry
Falconry is "the taking of wild quarry in its natural state and habitat by means of a trained raptor". There are two traditional terms used to describe a person involved in falconry: a falconer flies a falcon; an austringer flies a hawk or an eagle...
in Turkish; 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...
: Ali Kushgii), was a Turkic
Turkic peoples
The Turkic peoples are peoples residing in northern, central and western Asia, southern Siberia and northwestern China and parts of eastern Europe. They speak languages belonging to the Turkic language family. They share, to varying degrees, certain cultural traits and historical backgrounds...
or Persian astronomer
Islamic astronomy
Islamic astronomy or Arabic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age , and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa, and...
, mathematician
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...
and physicist
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,...
originally from 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...
, who settled in the Ottoman Empire
Ottoman Empire
The Ottoman EmpireIt was usually referred to as the "Ottoman Empire", the "Turkish Empire", the "Ottoman Caliphate" or more commonly "Turkey" by its contemporaries...
some time before 1472. As a disciple of Ulugh Beg
Ulugh Beg
Ulugh Bek was a Timurid ruler as well as an astronomer, mathematician and sultan. His commonly-known name is not truly a personal name, but rather a moniker, which can be loosely translated as "Great Ruler" or "Patriarch Ruler" and was the Turkic equivalent of Timur's Perso-Arabic title Amīr-e...
, he is best known for the development of 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...
independent from 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...
, and for providing empirical evidence for the Earth's rotation in his treatise, Concerning the Supposed Dependence of Astronomy upon Philosophy. In addition to his contributions to Ulugh Beg
Ulugh Beg
Ulugh Bek was a Timurid ruler as well as an astronomer, mathematician and sultan. His commonly-known name is not truly a personal name, but rather a moniker, which can be loosely translated as "Great Ruler" or "Patriarch Ruler" and was the Turkic equivalent of Timur's Perso-Arabic title Amīr-e...
's famous work Zij-i-Sultani
Zij-i-Sultani
Zīj-i Sultānī is a Zij astronomical table and star catalogue that was published by Ulugh Beg in 1437. It was the joint product of the work of a group of Muslim astronomers working under the patronage of Ulugh Beg at Samarkand's Ulugh Beg Observatory...
and to the founding of Sahn-ı Seman University, one of the first madrasahs in the Ottoman Empire, Ali Qushji was also the author of several scientific works and textbooks on astronomy.
Early life and works
Ali Qushji was born in 1403 in the city of SamarkandSamarkand
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...
, in present-day Uzbekistan
Uzbekistan
Uzbekistan , officially the Republic of Uzbekistan is a doubly landlocked country in Central Asia and one of the six independent Turkic states. It shares borders with Kazakhstan to the west and to the north, Kyrgyzstan and Tajikistan to the east, and Afghanistan and Turkmenistan to the south....
. His full name at birth was Ala al-Dīn Ali ibn Muhammed al-Qushji. The last name Qushji derived from the Turkish term kuşçu - the falconer - due to the fact that Ali's father Muhammad was the royal falconer
Falconry
Falconry is "the taking of wild quarry in its natural state and habitat by means of a trained raptor". There are two traditional terms used to describe a person involved in falconry: a falconer flies a falcon; an austringer flies a hawk or an eagle...
of Ulugh Beg
Ulugh Beg
Ulugh Bek was a Timurid ruler as well as an astronomer, mathematician and sultan. His commonly-known name is not truly a personal name, but rather a moniker, which can be loosely translated as "Great Ruler" or "Patriarch Ruler" and was the Turkic equivalent of Timur's Perso-Arabic title Amīr-e...
.
Jamshid al-Kashi
Ghiyāth al-Dīn Jamshīd Masʾūd al-Kāshī was a Persian astronomer and mathematician.-Biography:...
and Muin al-Dīn Kashi. He moved to Kerman, Iran (Persia) and there he conducted some researches on the storms of Oman sea. He completed Hall-e Eshkal-i Ghammar (Explanations of the Periods of the Moon) and Sharh-e Tajrid in Kirman. He moved to Herat and taught Molla Cami about astronomy (1423). After professing in Herat for a while he went back to Samarkand and herald his works about moon to Ulugh Beg. Ulugh Beg was fascinated with the works and read the entire work while standing up. Ulugh Beg assigned him to Ulugh Beg Observatory
Ulugh Beg Observatory
The Ulugh Beg Observatory is an observatory in Samarkand, Uzbekistan. Built in the 1420s by the Timurid astronomer Ulugh Beg, it is considered by scholars to have been one of the finest observatories in the Islamic world at the time and the largest in Central Asia before it was destroyed in 1449...
which was called "Samarkand Observatory" at that time. He worked there till Ulugh Beg was assassinated.
After Ulugh Beg's death, Ali Qushji went to Herat, Tashkent
Tashkent
Tashkent is the capital of Uzbekistan and of the Tashkent Province. The officially registered population of the city in 2008 was about 2.2 million. Unofficial sources estimate the actual population may be as much as 4.45 million.-Early Islamic History:...
and finally Tabriz
Tabriz
Tabriz is the fourth largest city and one of the historical capitals of Iran and the capital of East Azerbaijan Province. Situated at an altitude of 1,350 meters at the junction of the Quri River and Aji River, it was the second largest city in Iran until the late 1960s, one of its former...
, where around 1470, the Ak Koyunlu
Ak Koyunlu
The Aq Qoyunlu or Ak Koyunlu, also called the White Sheep Turkomans , was an Sunni Oghuz Turkic tribal federation that ruled parts of present-day Eastern Turkey, Armenia, Azerbaijan, northern Iraq, and Iran from 1378 to 1508.-History:According to chronicles from the Byzantine Empire, the Aq Qoyunlu...
ruler Uzun Hasan sent him as a delegate to the Ottoman Sultan Mehmed II
Mehmed II
Mehmed II , was Sultan of the Ottoman Empire for a short time from 1444 to September 1446, and later from...
. At that time Husayn Bayqarah
Husayn Bayqarah
Husayn Bayqarah was a Timurid ruler of Herat from 1469 to 1506, with a brief interruption in 1470. His father was Mansur, a great-grandson of Timur...
had come to reign in Herat but Qushji preferred Constantinople rather than Herat because of Sultan Mehmed's attitude toward scientists and intellectuals.
Constantinople era
When he came to Constantinople (present-day IstanbulIstanbul
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...
), his grandson Ghutb al-Dīn Muhammed had a son Mirim Chalabi who would be a great mathematician and astronomer in the future. Ali Qushji composed "risalah dar hay’at" in Persian
Persian language
Persian is an Iranian language within the Indo-Iranian branch of the Indo-European languages. It is primarily spoken in Iran, Afghanistan, Tajikistan and countries which historically came under Persian influence...
for Mehmed II
Mehmed II
Mehmed II , was Sultan of the Ottoman Empire for a short time from 1444 to September 1446, and later from...
at Constantinople in 1470. Also he wrote "Sharh e resalye Fathiyeh", "resalye Mohammadiye" in Constantinople, which are in Arabic
Arabic language
Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...
on the topic of mathematics. Qushji's work made a great impact on the scientific community. The work has thousands of copies in handwriting libraries all around the world.
He then finished "Sharh e tejrid" on Nasir al-Din al-Tusi
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...
's "Tejrid al-kalam". That work is called "Sharh e Jadid" in scientific community. It is considered as the most important philosophical work on metaphysics, physics, optics and mathematics done within Islamic civilization.
Contributions to astronomy
Qushji improved on Nasir al-Din al-TusiNasir 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...
's planetary model and presented an alternative planetary model for Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
. He was also one of the astronomers that were part of Ulugh Beg
Ulugh Beg
Ulugh Bek was a Timurid ruler as well as an astronomer, mathematician and sultan. His commonly-known name is not truly a personal name, but rather a moniker, which can be loosely translated as "Great Ruler" or "Patriarch Ruler" and was the Turkic equivalent of Timur's Perso-Arabic title Amīr-e...
's team of researchers working at the Samarqand observatory
Observatory
An observatory is a location used for observing terrestrial or celestial events. Astronomy, climatology/meteorology, geology, oceanography and volcanology are examples of disciplines for which observatories have been constructed...
and contributed towards the Zij-i-Sultani
Zij-i-Sultani
Zīj-i Sultānī is a Zij astronomical table and star catalogue that was published by Ulugh Beg in 1437. It was the joint product of the work of a group of Muslim astronomers working under the patronage of Ulugh Beg at Samarkand's Ulugh Beg Observatory...
compiled there. In addition to his contributions to Zij, Ali Qushji wrote nine works in astronomy, two of them in Persian
Persian language
Persian is an Iranian language within the Indo-Iranian branch of the Indo-European languages. It is primarily spoken in Iran, Afghanistan, Tajikistan and countries which historically came under Persian influence...
and seven in Arabic
Arabic language
Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...
. A 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...
translation of two of Qushji's works, the Tract on Arithmetic and Tract on Astronomy, was published by John Greaves
John Greaves
John Greaves was an English mathematician, astronomer and antiquary.-Life:He was born in Colemore, near Alresford, Hampshire. He was the eldest son of John Greaves, rector of Colemore, and Sarah Greaves...
in 1650.
Concerning the Supposed Dependence of Astronomy upon Philosophy
Qushji's most important astronomical work is Concerning the Supposed Dependence of Astronomy upon Philosophy. Under the influence of Islamic theologiansIslamic 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...
who opposed 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, Qushji rejected 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 completely separated 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 Islamic astronomy
Islamic astronomy
Islamic astronomy or Arabic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age , and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa, and...
, 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
Science
Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe...
. This allowed him to explore alternatives to the Aristotelian notion of a stationary Earth, as he explored the idea of a moving Earth instead. Though Savage-Smith asserts that no Islamic astronomers proposed a heliocentric universe. He found 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 through his observation on 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 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.
His predecessor al-Tusi had previously realized that "the monoformity of falling bodies, and the uniformity of celestial motions," both moved “in a single way,” though he still relied on Aristotelian physics to provide "certain principles that only the natural philosophers could provide the astronomer." Qushji took this concept further and proposed that "the astronomer had no need for Aristotelian physics and in fact should establish his own physical principles independently of the natural philosophers." Alongside his rejection of Aristotle's concept of a stationary Earth, Qushji suggested that there was no need for astronomers to follow the Aristotelian notion of the heavenly bodies moving in 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...
.
Qushji's 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...
. This is considered to be a "conceptual revolution" that had no precedent in European astronomy prior to the Copernican Revolution
Copernican Revolution
The Copernican Revolution refers to the paradigm shift away from the Ptolemaic model of the heavens, which postulated the Earth at the center of the galaxy, towards the heliocentric model with the Sun at the center of our Solar System...
in the 16th century. Qushji's view on the Earth's motion was similar to the later views of 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....
on this issue, though it is uncertain whether the former had any influence on the latter. However, it is likely that they both may have arrived at similar conclusions due to using the earlier work of Nasir al-Din al-Tusi
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...
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."
Astronomy
- Sharh e Zîj e Ulugh Beg (In Persian)
- Resale fi Halle Eshkale Moadeleye Ghamar lil-Masir (Faide fi Eshkâli Utared)
- Resale fi Asli'l-HâricYumkin fi's-Sufliyyeyn
- Sharh ‘ale't-Tuhfeti'sh-Shâhiyye fi al-Heyat
- Resale dar elm-i Heyat (In Persian)
- el-Fathiyye fî elm al-Heyat (In Arabic)
- Resale fi Hall-e Eshkal-i Ghammar (In Persian)
- Concerning the Supposed Dependence of Astronomy upon Philosophy
Mathematics
- Resaletu'l-Muhammediyye fi-Hesab (In Persian)
- Resale dar elm-e Hesab: Suleymaniye
Kalam and Fiqh
- Sharh e Jadid ale't-Tejrîd
- Hashiye ale't-Telvîh
- Unkud-üz-Zevahir fi Nazm-al-Javaher
Linguistics
- Sharh Risâleti'l-Vadiyye
- El-Ifsâh
- El-Unkûdu'z-Zevâhir fî Nazmi'l-Javâher
- Sharh e'Sh-Shâfiye
- Resale fî Beyâni Vadi'l-Mufredât
- Fâ'ide li-Tahkîki Lâmi't-Ta'rîf
- Resale mâ Ene Kultu
- Resale fî'l-Hamd
- Resale fî Ilmi'l-Me'ânî
- Resale fî Bahsi'l-Mufred
- Resale fî'l-Fenni's-Sânî min Ilmihal-Beyân
- Tafsir e-Bakara ve Âli Imrân
- Risâle fî'l-İstişâre
- Mahbub-al-Hamail fi kashf-al-mesail
- Tajrid-al-Kalam