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Alessandro Algardi

Alessandro Algardi (July 31, 1598 – June 10, 1654) was an Italian high-Baroque sculptor active almost exclusively in Rome. In the latter decades of his life, he was, along with Francesco Borromini and Pietro da Cortona, one of the major rivals of Gian Lorenzo Bernini, in Rome. He is now most admired for his portrait busts that have great vivacity and dignity.

Early years
Algardi was born in Bologna, where at a young age, he was apprenticed in the studio of Agostino Carracci. However, his aptitude for sculpture led him to work for Giulio Cesare Conventi (1577–1640), an artist of modest talents. His two earliest known works date back to this period: two statues of saints, made of chalk, in the Oratory of Santa Maria della Vita in Bologna. By the age of twenty, Ferdinando I, Duke of Mantua, began commissioning works from him, and he was also employed by local jewelers for figurative designs. After a short residence in Venice, he went to Rome in 1625 with an introduction from the Duke of Mantua to the late pope's nephew, Cardinal Ludovico Ludovisi, who employed him for a time in the restoration of ancient statues.

Tomb of Pope Leo XI
Propelled by the Borghese and Barberini patronage, Gian Lorenzo Bernini and his studio garnered most of the major Roman sculptural commissions. For nearly a decade, Algardi struggled for recognition. In Rome he was aided by friends that included Pietro da Cortona and his fellow Bolognese, Domenichino. His early Roman commissions included terracotta and some marble portrait busts, while he supported himself with small works like crucifixes. In the 1630s he worked on the tombs of the Mellini family in the Mellini Chapel in Santa Maria del Popolo.

Algardi's first major commission came about in 1634, when Cardinal Ubaldini (Medici) contracted for a funeral monument for his great-uncle, Pope Leo XI, the third of the Medici popes, who had reigned for less than a month in 1605. The monument was started in 1640, and mostly completed by 1644. The arrangement mirrors the one designed by Bernini for the Tomb of Urban VIII (1628–47), with a central hieratic sculpture of the pope seated in full regalia and offering a hand of blessing, while at his feet, two allegorical female figures flank his sarcophagus. However, in Bernini's tomb, the vigorous upraised arm and posture of the pope is counterbalanced by an active drama below, wherein the figures of Charity and Justice are either distracted by putti or lost in contemplation, while skeletal Death actively writes the epitaph. Algardi's tomb is much less dynamic. The allegorical figures of Magnanimity and Liberality have an impassive, ethereal dignity. Some have identified the helmeted figure of Magnanimity with that of Athena and iconic images of Wisdom. Liberality resembles Duquesnoy's famous Santa Susanna, but rendered more elegant. The tomb is somberly monotone and lacks the polychromatic excitement that detracts from the elegiac mood of Urban VIII's tomb.

In 1635–38, Pietro Boncompagni commissioned from Algardi a colossal statue of Philip Neri with kneeling angels for Santa Maria in Vallicella, completed in 1640. Immediately after this, Algardi produced a sculptural group of the beheading of Saint Paul with two figures: a kneeling, resigned saint and the executioner poised to strike the sword-blow, for the church of San Paolo, Bologna. These works established his reputation, alongside two reliefs of The Martyrdom of St Paul and The Rest on the Flight into Egypt (a contemporary replica of the latter is now in the Victoria and Albert Museum). Like Bernini's characteristic works, they often express the Baroque aesthetic of depicting dramatic attitudes and emotional expressions, yet Algardi's sculpture has a restraining sobriety in contrast to those of his rival.

Papal favour under Innocent X and Spanish commissions

With the death of the Barberini Pope Urban VIII in 1644 and the accession of the Pamphilj Pope Innocent X, the Barberini family and fell into disrepute, resulting in fewer commissions for Bernini. Algardi, on the other hand, was embraced by the new pope and the pope's nephew, Camillo Pamphilj. Algardi's portraits were highly prized, and their formal severity contrasts with Bernini's more vivacious expression. A large hieratic bronze of Innocent X by Algardi is now to be found in the Capitoline Museums.

Algardi was not renowned for his architectural abilities. Although he was in charge of the project for the papal villa, the Villa Pamphili, now Villa Doria Pamphili, outside the Porta San Pancrazio in Rome, he may have had professional guidance on the design of the casino from the architect/engineer Girolamo Rainaldi and help with supervising its construction from his assistant Giovanni Francesco Grimaldi. The casino was a showcase for the Pamphili collection of sculpture, ancient and contemporary, on which Algardi was well able to advise. In the villa grounds, Algardi and his studio executed sculpture-encrusted fountains and other garden features, where some of his free-standing sculpture and bas-reliefs remain.

In 1650 Algardi met Diego Velázquez, who obtained commissions for his work from Spain. As a consequence there are four chimney-pieces by Algardi in the Royal Palace of Aranjuez, and in the gardens, the figures on the fountain of Neptune are also by him. The Augustinian monastery at Salamanca contains the tomb of the Count and Countess de Monterey, another work by Algardi.

Fuga d'Attila relief
Algardi's large, dramatic, high-relief marble panel of Pope Leo and Attila, created from 1646 to 1653, is commonly referred to as Fuga d'Attila or Flight of Attila. It was created for St Peter's Basilica, and it reinvigorated the use of such marble reliefs. There had been large marble reliefs used previously in Roman churches, but for most patrons, sculpted marble altarpieces were far too costly. In this relief, the two principal figures, the stern and courageous pope and the dismayed and frightened Attila, surge forward from the center into three dimensions. Only they two see the descending angelic warriors rallying to the pope's defense, while all others in the background reliefs, persist in performing their respective earthly duties.

The subject was apt for a papal state seeking to increase its power, since it depicts the historical legend wherein Saint Leo the Great, the first pope to receive the epithet, with supernatural aid, deterred the Huns from looting Rome. From a baroque standpoint, the incident is common theme: a moment of divine intervention in the affairs of man. Algardi's patron's message through the relief would be that all viewers should be sternly reminded of the papal capacity to invoke divine retribution against enemies.

In his later years Algardi controlled a large studio and amassed a great fortune. Algardi's classicizing manner was carried on by pupils, including Ercole Ferrata and Domenico Guidi, and Antonio Raggi initially trained with him. The latter two completed his design for an altarpiece of the Vision of Saint Nicholas at San Nicola da Tolentino, Rome, using two separate marble pieces linked together in one event and place, yet successfully separating the divine and earthly spheres. Other lesser known assistants from his studio include Francesco Barrata, Girolamo Lucenti, and Giuseppe Peroni.

Algardi died in Rome within a year of completing his famous relief, which was admired by contemporaries.

Critical assessment and legacy
Algardi was also known for his portraiture which shows an obsessive attention to details of psychologically revealing physiognomy in a sober but immediate naturalism, and minute attention to costume and draperies, such as in the busts of Laudivio Zacchia, Camillo Pamphilj, and of Muzio Frangipane and his two sons Lello and Roberto.

In temperament, his style was more akin to the classicized and restrained baroque of Duquesnoy than to the emotive works of other baroque artists. From an artistic point of view, he was most successful in portrait-statues and groups of children, where he was obliged to follow nature most closely. His terracotta models, some of them finished works of art, were prized by collectors. An outstanding series of terracotta models is at the Hermitage Museum, Saint Petersburg.

title: Alessandro Algardi


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Alger of Liège

Alger of Liège (1055–1131), known also as Alger of Cluny and Algerus Magister, was a learned clergyman and canonist from Liège, author of several notable works.

Alger was first deacon and scholaster of church of St Bartholomew in his native Liège and was then appointed (c. 1100) as a canon in St. Lambert's Cathedral. Moreover, he acted as the personal secretary of bishop Otbert from 1103. He declined offers from German bishops and finally retired to the monastery of Cluny after 1121, where he died at a high age, leaving behind a solid reputation for piety and intelligence.

He played a leading role in the trial of Rupert of Deutz in 1116.

His History of the Church of Liège, and many of his other works, are lost. The most important remaining are:
 * 1) De Misericordia et Justitia (On Mercy and Justice), a collection of biblical extracts and sayings of Church Fathers with commentary (an important work for the history of church law and discipline), which is to be found in the Anecdota of Martène, vol. v. This work has been suggested as influential on Gratian's  Decretum
 * 2) De Sacramentis Corporis et Sanguinis Domini; a treatise, in three books, against the Berengarian heresy, highly commended by Peter of Cluny and Erasmus, who published it in 1530. In this book, Alger also took on Rupert of Deutz' views on the Eucharist and predestination.
 * 3) De Gratia et Libero Arbitrio; given in Bernard Pez's Anecdota, vol. iv.
 * 4) De Sacrificio Missae; given in the Collectio Scriptor. Vet. of Angelo Mai, vol. ix. p. 371.
 * 5) De dignitate ecclesie Leodiensis, which established the reciprocal obligations of the primary and secondary churches; inserted in the Liber officiorum ecclesie Leodiensis (1323).

A biography was written by Nicholas of Liège: De Algero veterum testimonia.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Alger of Liège


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Algiers

Algiers (الجزائر) is the capital and largest city of Algeria, located in the north-central part of the country. The city's population at the 2008 census was 2,988,145 and in 2020 was estimated to be around 4,500,000.

Algiers is situated on the west side of the Bay of Algiers, in the Mediterranean Sea. The modern part of the city is built on the level ground by the seashore; the old part, the ancient city of the deys, climbs the steep hill behind the modern town and is crowned by the Casbah or citadel (a UNESCO World Heritage Site), 122 m above the sea. The Casbah and the two quays form a triangle.

Names
The city's name is derived via French and Catalan Alger from the Arabic name al-Jazāʾir (الجزائر), "The Islands". This name refers to the four former islands which lay off the city's coast before becoming part of the mainland in 1525. Al-Jazāʾir is itself a truncated form of the city's older name Jazaʾir Banī Mazghanna (جزائر بني مزغانة), "islands of Banu Mazghanna", used by early medieval geographers such as Muhammad al-Idrisi and Yaqut al-Hamawi. The name was given by Buluggin ibn Ziri after he established the city on the ruins of the Phoenician city of Icosium in 950. During Ottoman rule, the name of the capital, al-Jazā'ir, was extended over the entire country, giving it the English name Algeria derived from the French name Algérie.

In classical antiquity, the ancient Greeks knew the town as Ikósion (Ἰκόσιον), which was Latinized as Icosium under Roman rule. The Greeks explained the name as coming from their word for "twenty" (εἴκοσι, eíkosi), supposedly because it had been founded by 20 companions of Hercules when he visited the Atlas Mountains during his labors.

Algiers is also known as el-Behdja (البهجة, "The Joyous") or "Algiers the White" (Alger la Blanche) for its whitewashed buildings.

Early history
The city's earliest history was as a small port in Carthage where Phoenicians were trading with other Mediterraneans. After the Punic Wars, the Roman Republic eventually took over administration of the town, which they called Icosium. Its ruins now form part of the modern city's marine quarter, with the Rue de la Marine following a former Roman road. Roman cemeteries existed near Bab-el-Oued and Bab Azoun. The city was given Latin rights by the emperor Vespasian. The bishops of Icosium are mentioned as late as the 5th century, but the ancient town fell into obscurity during the Muslim conquest of the Maghreb.

The present city was founded in 944 by Buluggin ibn Ziri, the founder of the Berber Zirid dynasty. He had built his own house and a Sanhaja center at Ashir in 935 just south of Algiers. Although the Zirid dynasty was overthrown by Roger II of Sicily in 1148, the Zirids had already lost control of Algiers to their cousins the Hammadids in 1014.

The city was wrested from the Hammadids by the Almohad Caliphate in 1159, and in the 13th century came under the dominion of the Ziyanid sultans of the Kingdom of Tlemcen. Nominally part of the sultanate of Tlemcen, Algiers had a large measure of independence under Thaaliba amirs of its own due to Oran being the chief seaport of the Ziyanids.

The Peñón of Algiers, an islet in front of Algiers harbour, had been occupied by the Spaniards as early as 1302. Thereafter, a considerable amount of trade began to flow between Algiers and Spain. However, Algiers continued to be of comparatively little importance until after the expulsion of the Moors from Spain, many of whom sought asylum in the city. In 1510, following their occupation of Oran and other towns on the coast of Africa, the Spaniards fortified the islet of Peñon and imposed a levy intended to suppress the Barbary pirates.

Ottoman rule
In 1516, the amir of Algiers, Selim b. Teumi, invited the corsair brothers Oruç Reis and Hayreddin Barbarossa to expel the Spaniards. Oruç Reis came to Algiers, ordered the assassination of Selim, and seized the town and ousted the Spanish in the Capture of Algiers (1516). Hayreddin, succeeding Oruç after the latter was killed in battle against the Spaniards in the 1518 fall of Tlemcen, was the founder of the pashaluk, which subsequently became the beylik, of Algeria. Barbarossa lost Algiers in 1524 but regained it with the 1529 Capture of Peñón of Algiers, and then formally invited the Sultan Suleiman the Magnificent to accept sovereignty over the territory and to annex Algiers to the Ottoman Empire.

Algiers from this time became the chief seat of the Barbary pirates. In October 1541 in the Algiers expedition, the King of Spain and Charles V, Holy Roman Emperor sought to capture the city, but a storm destroyed a great number of his ships, and his army of some 30,000, chiefly made up of Spaniards, was defeated by the Algerians under their pasha, Hassan.

Formally part of the Ottoman Empire but essentially free from Ottoman control, starting in the 16th century Algiers turned to piracy and ransoming. Due to its location on the periphery of both the Ottoman and European economic spheres, and depending for its existence on a Mediterranean that was increasingly controlled by European shipping, backed by European navies, piracy became the primary economic activity. Repeated attempts were made by various nations to subdue the pirates that disturbed shipping in the western Mediterranean and engaged in slave raids as far north as Iceland. By the 17th century, up to 40% of the city's 100,000 inhabitants were enslaved Europeans. The United States fought two wars (the First and Second Barbary Wars) over Algiers' attacks on shipping.

Among the notable people held for ransom was the future Spanish novelist, Miguel de Cervantes, who was held captive in Algiers for almost five years, and wrote two plays set in Algiers of the period. The primary source for knowledge of Algiers of this period, since there are no contemporary local sources, is the Topografía e historia general de Argel (1612, but written earlier), published by Diego de Haedo, but whose authorship is disputed. This work describes in detail the city, the behavior of its inhabitants, and its military defenses, with the unsuccessful hope of facilitating an attack by Spain so as to end the piracy.

A significant number of renegades lived in Algiers at the time, Christians converted voluntarily to Islam, many fleeing the law or other problems at home. Once converted to Islam, they were safe in Algiers. Many occupied positions of authority, such as Samson Rowlie, an Englishman who became Treasurer of Algiers.

The city under Ottoman control was enclosed by a wall on all sides, including along the seafront. In this wall, five gates allowed access to the city, with five roads from each gate dividing the city and meeting in front of the Ketchaoua Mosque. In 1556, a citadel was constructed at the highest point in the wall. A major road running north to south divided the city in two: The upper city (al-Gabal, or 'the mountain') which consisted of about fifty small quarters of Andalusian, Jewish, Moorish and Kabyle communities, and the lower city (al-Wata, or 'the plains') which was the administrative, military and commercial centre of the city, mostly inhabited by Ottoman Turkish dignitaries and other upper-class families.

In August 1816, the city was bombarded by a British squadron under Lord Exmouth (a descendant of Thomas Pellew, taken in an Algerian slave raid in 1715 ), assisted by men-of-war from the Kingdom of the Netherlands, destroying the corsair fleet harboured in Algiers.

French rule
The history of Algiers from 1830 to 1962 is bound to the larger history of Algeria and its relationship to France. On July 4, 1830, under the pretext of an affront to the French consul—whom the dey had hit with a fly-whisk when the consul said the French government was not prepared to pay its large outstanding debts to two Algerian merchants—a French army under General de Bourmont attacked the city in the 1830 invasion of Algiers. The city capitulated the following day. Algiers became the capital of French Algeria.

Many Europeans settled in Algiers, and by the early 20th century they formed a majority of the city's population. During the 1930s, the architect Le Corbusier drew up plans for a complete redesign of the colonial city. Le Corbusier was highly critical of the urban style of Algiers, describing the European district as "nothing but crumbling walls and devastated nature, the whole a sullied blot". He also criticised the difference in living standards he perceived between the European and African residents of the city, describing a situation in which "the 'civilised' live like rats in holes" whereas "the 'barbarians' live in solitude, in well-being". However, these plans were ultimately ignored by the French administration.

During World War II, Algiers was the first city to be seized from the Axis by the Allies in Operation Terminal, a part of Operation Torch.

In 1962, after a bloody independence struggle in which hundreds of thousands (estimates range between 350,000 and 1,500,000) died (mostly Algerians but also French and Pieds-Noirs) during fighting between the French Army and the Algerian Front de Libération Nationale, Algeria gained its independence, with Algiers as its capital. Since then, despite losing its entire pied-noir population, the city has expanded massively. It now has about five million inhabitants, or 10 percent of Algeria's population—and its suburbs now cover most of the surrounding Mitidja plain.

Algerian War
Algiers also played a pivotal role in the Algerian War (1954–1962), particularly during the Battle of Algiers when the 10th Parachute Division of the French Army, starting on January 7, 1957, and on the orders of the French Minister of Justice François Mitterrand (who authorized any means "to eliminate the insurrectionists"), led attacks against the Algerian fighters for independence. Algiers remains marked by this battle, which was characterized by merciless fighting between FLN forces which carried out a guerrilla campaign against the French military and police and pro-French Algerian soldiers, and the French Army which responded with a bloody repression, torture and blanket terrorism against the native population. The demonstrations of May 13 during the crisis of 1958 provoked the fall of the Fourth Republic in France, as well as the return of General de Gaulle to power.

Independence
Algeria achieved independence on July 5, 1962. Run by the FLN that had secured independence, Algiers became a member of Non-Aligned Movement during the Cold War. In October 1988, one year before the fall of the Berlin Wall, Algiers was the site of demonstrations demanding the end of the single-party system and the creation of a real democracy baptized the "Spring of Algier". The demonstrators were repressed by the authorities (more than 300 dead), but the movement constituted a turning point in the political history of modern Algeria. In 1989, a new constitution was adopted that put an end to the one-party rule and saw the creation of more than fifty political parties, as well as official freedom of the press.

Crisis of the 1990s
The city became the theatre of many political demonstrations of all descriptions until 1993. In 1991, a political entity dominated by religious conservatives called the Islamic Salvation Front engaged in a political test of wills with the authorities. In the 1992 elections for the Algerian National Assembly, the Islamists garnered a large amount of support in the first round. Fearing an eventual win by the Islamists, the army canceled the election process, setting off a civil war between the State and armed religious conservatives which would last for a decade.

On December 11, 2007, two car bombs exploded in Algiers. One bomb targeted two United Nations office buildings and the other targeted a government building housing the Supreme Court. The death toll was at least 62, with over two hundred injured in the attacks. However, only 26 remained hospitalized the following day. , it is speculated that the attack was carried out by the Al Qaida cell within the city.

Indigenous terrorist groups have been actively operating in Algeria since around 2002.

Districts of Algiers

 * The Casbah (of Al Qasbah, "the Citadel"), 1st District of Algiers: called Al-Djazaïr Al Mahroussa ("Well Kept Algiers"), is founded on the ruins of old Icosium. It is a small city of picturesque winding lanes built on a hill and descending towards the sea, divided into two sections: the High City and the Low City. It includes 17th-century buildings: Ketchaoua Mosque (rebuilt in the 18th century by the Dey Baba Hassan), El Djedid Mosque (built in 1660, at the time of Turkish regency), El Kebir Mosque (oldest of the mosques, built by Almoravid Youssef Ibn Tachfin and rebuilt in 1794), the Ali Bitchin Mosque (Raïs, 1623), and Dar Aziza, formerly part of the Palace of Jénina.
 *  Bab El Oued: Literally the River's Gate, the popular district which extends from the Casbah beyond "the gate of the river". It is the capital's darling and best liked borough. Famous for its square with "the three clocks" and for its "market Triplet", it is also a district of workshops and manufacturing plants.
 *  Edge of sea: from 1840, the architects Pierre-August Guiauchain and Charles Frédéric Chassériau designed new buildings apart from the Casbah, town hall, law courts, buildings, theatre, palace of the Governor, and casino, to form an elegant walk bordered by arcades which is today the boulevard Che Guevara (formerly the Boulevard of the Republic).
 *  Kouba (will daira of Hussein-dey): Kouba is an old village which was absorbed by the expansion of the town of Algiers. Kouba quickly developed under the French colonial era then continued growing due to formidable demographic expansion that Algiers saw after the independence of Algeria in 1962. It is today a district of Algiers which is largely made up of houses, villas, and buildings not exceeding five stories.
 * El Harrach, a suburb of Algiers, is located about 10 km to the east of the city.
 * The communes of Hydra, Ben Aknoun, El-Biar and Bouzareah form what the inhabitants of Algiers call the "Heights of Algiers". These communes shelter the majority of the foreign embassies of Algiers, of many ministries and university centres, which makes it one of the administrative and policy centres of the country.
 * The Didouche Mourad street is located in the 3rd district Of Algiers. It extends from the Grande Post office to the Heights of Algiers. It crosses in particular the place Audin, the Faculty of Algiers, The Crowned Heart and the Freedom Park (formerly Galland). It is bordered by smart stores and restaurants along most of its length. It is regarded as the heart of the capital.

Climate
Algiers has a Mediterranean climate (Köppen climate classification Csa). Its proximity to the Mediterranean Sea aids in moderating the city's temperatures. As a result, Algiers usually does not see the extreme temperatures that are experienced in the adjacent interior. Algiers on average receives roughly 600 mm of rain per year, the bulk of which is seen between October and April. The precipitation is higher than in most of coastal Mediterranean Spain, and similar to most of coastal Mediterranean France, as opposed to the interior North African semi-arid or arid climate.

Snow is very rare; in 2012, the city received 100 mm of snowfall, its first snowfall in eight years.

Climate change
A 2019 paper published in PLOS One estimated that under Representative Concentration Pathway 4.5, a "moderate" scenario of climate change where global warming reaches ~2.5-3 C-change by 2100, the climate of Algiers in the year 2050 would most closely resemble the current climate of Perth in Australia. The annual temperature would increase by 2.6 C-change, and the temperature of the warmest month by 1.9 C-change, while the temperature of the coldest month would be 3.8 C-change higher. According to Climate Action Tracker, the current warming trajectory appears consistent with 2.7 C-change, which closely matches Representative Concentration Pathway (RCP) 4.5.

Moreover, according to the 2022 IPCC Sixth Assessment Report, Algiers is one of 12 major African cities (Abidjan, Alexandria, Algiers, Cape Town, Casablanca, Dakar, Dar es Salaam, Durban, Lagos, Lomé, Luanda and Maputo) which would be the most severely affected by the future sea level rise. It estimates that they would collectively sustain cumulative damages of U$65 billion under RCP 4.5 and US$86.5 billion for the high-emission scenario RCP 8.5 by the year 2050. Additionally, RCP 8.5 combined with the hypothetical impact from marine ice sheet instability at high levels of warming would involve up to US$137.5 billion in damages, while the additional accounting for the "low-probability, high-damage events" may increase aggregate risks to $187 billion for the "moderate" RCP 4.5, $206 billion for RCP 8.5 and $397 billion under the high-end ice sheet instability scenario. Since sea level rise would continue for about 10,000 years under every scenario of climate change, future costs of sea level rise would only increase, especially without adaptation measures. The Casbah is on a list of 10 African World Heritage Site most threatened by sea level rise.

Government
The city (and province) of Algiers is composed of 13 administrative districts, sub-divided into 57 communes listed below with their populations at the 1998 and 2008 Censuses:

Local architecture

There are many public buildings of interest, including the whole Kasbah quarter, Martyrs Square (Sahat ech-Chouhada ساحة الشهداء), the government offices (formerly the British consulate), the "Grand", "New", and Ketchaoua Mosques, the Roman Catholic cathedral of Notre Dame d'Afrique, the Bardo Museum, the old Bibliothèque Nationale d'Alger—a moorish palace built in 1799–1800 and the new National Library, built in a style reminiscent of the British Library.

The main building in the Kasbah was begun in 1516 on the site of an older building, and served as the palace of the deys until the French conquest. A road has been cut through the centre of the building, the mosque turned into barracks, and the hall of audience allowed to fall into ruin. There still remain a minaret and some marble arches and columns. Traces exist of the vaults in which were stored the treasures of the dey.

Djamaa el Kebir (Jamaa-el-Kebir الجامع الكبير) is the oldest mosque in Algiers. It was first built by Yusuf ibn Tashfin, but reconstructed many times. The pulpit (minbar منبر) bears an inscription showing that the building existed in 1097. The minaret was built by the sultan of Tlemcen, in 1324. The interior of the mosque is square and is divided into aisles by columns joined by Moorish arches.

The New Mosque (Jamaa-el-Jedid الجامع الجديد), dating from the 17th century, is in the form of a Greek cross, surmounted by a large white cupola, with four small cupolas at the corners. The minaret is 27 m high. The interior resembles that of the Grand Mosque.

The church of the Holy Trinity (built in 1870) stands at the southern end of the rue d'Isly near the site of the demolished Fort Bab Azoun باب عزون. The interior is richly decorated with various coloured marbles. Many of these marbles contain memorial inscriptions relating to the British residents (voluntary and involuntary) of Algiers from the time of John Tipton, the first English consul, in 1580 (NB Some sources give 1585). One tablet records that in 1631 two Algerine pirate crews landed in Ireland, sacked Baltimore, and enslaved its inhabitants.

The Ketchaoua Mosque (Djamaa Ketchaoua جامع كتشاوة), at the foot of the Casbah, was before independence in 1962 the cathedral of St Philippe, itself made in 1845 from a mosque dating from 1612. The principal entrance, reached by a flight of 23 steps, is ornamented with a portico supported by four black-veined marble columns. The roof of the nave is of Moorish plaster work. It rests on a series of arcades supported by white marble columns. Several of these columns belonged to the original mosque. In one of the chapels was a tomb containing the bones of Geronimo. The building seems a curious blend of Moorish and Byzantine styles.

Algiers possesses a college with schools of law, medicine, science and letters. The college buildings are large and handsome. The Bardo Museum holds some of the ancient sculptures and mosaics discovered in Algeria, together with medals and Algerian money.

The port of Algiers is sheltered from all winds. There are two harbours, both artificial—the old or northern harbour and the southern or Agha harbour. The northern harbour covers an area of 95 ha. An opening in the south jetty affords an entrance into Agha harbour, constructed in Agha Bay. Agha harbour has also an independent entrance on its southern side. The inner harbour was begun in 1518 by Khair-ad-Din Barbarossa (see History, below), who, to accommodated his pirate vessels, caused the island on which was Fort Penon to be connected with the mainland by a mole. The lighthouse which occupies the site of Fort Penon was built in 1544.

Algiers was a walled city from the time of the deys until the close of the 19th century. The French, after their occupation of the city (1830), built a rampart, parapet and ditch, with two terminal forts, Bab Azoun باب عزون to the south and Bab-el-Oued اد to the north. The forts and part of the ramparts were demolished at the beginning of the 20th century, when a line of forts occupying the heights of Bouzareah بوزريعة (at an elevation of 396 m above the sea) took their place.

Notre Dame d'Afrique, a church built (1858–1872) in a mixture of the Roman and Byzantine styles, is conspicuously situated overlooking the sea, on the shoulder of the Bouzareah hills, 3 km to the north of the city. Above the altar is a statue of the Virgin depicted as a black woman. The church also contains a solid silver statue of the archangel Michael, belonging to the confraternity of Neapolitan fishermen.

Villa Abd-el-Tif, former residence of the dey, was used during the French period, to accommodate French artists, chiefly painters, and winners of the Abd-el-Tif prize, among whom Maurice Boitel, for a while of two years. Nowadays, Algerian artists are back in the villa's studios.

Monuments

 * Notre Dame d'Afrique, accessible by one cable car, is one of the city's most outstanding monuments: located in the district of Z' will ghara, the basilica was built around 1858.
 * Monument des Martyrs (Marquand E' chahid): an iconic concrete monument commemorating the Algerian war for independence. The monument was opened in 1982 on the 20th anniversary of Algeria's independence. It is fashioned in the shape of three standing palm leaves which shelter the "Eternal Flame" beneath. At the edge of each palm leaf stands a statue of a soldier, each representing a stage of Algeria's struggle.
 * The El Jedid mosque at the Place des Martyrs near the port.
 * Place of the Emir Abdelkader (formerly Bugeaud): in memory of the famous emir Abd El-Kader, resistant during French conquest of Algeria.
 * Grand Post Office (1910, by Voinot and Tondoire): construction of the neo-Moorish type which is in full centre town of Algiers.
 * The Jardin d'essai (Garden of Test; El-Hamma): situated in the east of Algiers, it extends over 80 ha and contains exotic plants and gardens. It was created in 1832 by A. Hardy.
 * Villa Abd-el-Hair, with the top of the Garden of test, one of the old residences of the dey, where until 1962, were placed the artists prizes winner of Price Abd-el-Hair, and in particular Maurice Boitel and Andre Hamburg.
 * Citadel.
 * Riadh El-Feth (shopping centre and art gallery).
 * Ketchaoua Mosque (This mosque became the Saint-Philippe cathedral during colonization before becoming again a mosque).
 * National Library, is in the district of El HAMMA and was built in the 1990s.
 * Djamaa el Kebir at the Rue de la Marine. It is the oldest mosque of Algiers and was built during the reign of the Almoravid sultan Yusuf ibn Tashfin.
 * Le Bastion 23 – Palais des Rais, built in 1576 by Dey Ramdhan Pacha and located in the lower Casbah in the Bab El Oued neighborhood.

Demographics
As of 2012, Algiers has a population of about 3,335,418.

The ethnic distribution is 53% from an Arabic-speaking background, 44% from a Berber-speaking background and 3% foreign-born.

Economy
Algiers is an important economic, commercial and financial center, with a stock exchange capitalized at 60 million euros. The city has the highest cost of living of any city in North Africa, as well as the 50th highest worldwide, as of March 2007, having gained one position compared to the previous year.

Mohamed Ben Ali El Abbar, president of the Council of Administration of the Emirate Group EMAAR, presented five "megaprojects" to Algerian President Abdelaziz Bouteflika, during a ceremony which took place Saturday, July 15, in the People's Palace of Algiers. These projects will transform the city of Algiers and its surroundings by equipping them with a retail area and restoration and leisure facilities.

The first project will concentrate on the reorganization and the development of the infrastructures of the railway station "Aga" located in the downtown area. The ultramodern station intended to accommodate more than 80.000 passengers per day, will become a centre of circulation in the heart of the grid system, surrounded by commercial offices and buildings and hotels intended for travellers in transit. A shopping centre and three high-rise office buildings rising with the top of the commercial zone will accompany the project.

The second project will not relate to the bay of Algiers and aims to revitalize the sea front. The development of the 44 km sea front will include marinas, channels, luxury hotels, offices, apartments of great standing, luxury stores and leisure amenities. A crescent-shaped peninsula will be set up on the open sea. The project of the bay of Algiers will also comprise six small islands, of which four of round form, connected to each other by bridges and marinas and will include tourist and residential complexes. The third project will relate to restructuring an area of Algiers, qualified by the originators of the project of "city of wellness". El Abbar indicated to the journalists that the complex would be "agreeable for all those which will want to combine tourism and well-being or tourism and relaxation". The complex will include a university, a research center and a medical centre. It should also include a hospital complex, a care centre, a hotel zone, an urban centre and a thermal spa with villas and apartments. The university will include a medical school and a school for care male nurses which will be able to accommodate 500 students. The university campus will have the possibility of seeing setting up broad ranges of buildings of research laboratories and residences.

Another project relates to technological implantation of a campus in Sidi Abdellah, 25 km south-east from Algiers. This 90 ha site will include shopping centres, residential zones with high standard apartments and a golf course surrounded by villas and hotels. Two other residential zones, including 1.800 apartments and 40 high standard villas, will be built on the surrounding hills.

The fifth project is that of the tourist complex Colonel Abbès, which will be located 25 km west from Algiers. This complex will include several retail zones, meeting places, and residential zones composed of apartments and villas with views of the sea.

There is another project under construction, by the name of Algiers Medina. The first step of the project is nearly complete.

A Hewlett-Packard office for French-speaking countries in Africa is in Algiers.

Tourist installations

Some 20 km to the west of Algiers are such seaside resorts as Sidi Fredj (ex-Sidi Ferruch), Palm Beach, Douaouda, Zéralda, and the Club of the Pines (residence of State); there are tourist complexes, Algerian and other restaurants, souvenir shops, supervised beaches, and other amenities. The city is also equipped with important hotel complexes such as the hotel Hilton, El-Aurassi or El Djazair. Algiers also has the first water park in the country. The tourism of Algiers is growing but is not as developed as that of the larger cities in Morocco or Tunisia.

Education
The presence of a large diplomatic community in Algiers prompted the creation of multiple international educational institutions. These schools include :

 * American International School of Algiers;
 * British School Algiers
 * El Kalimat School (English-language school);
 * Lycée International Alexandre-Dumas d'Alger (French school);
 * Roma Italian School of Algiers;
 * Russian Embassy School in Algiers.

There was formerly the École japonaise d'Alger (アルジェ日本人学校 Aruje Nihonjin Gakkō), a school for Japanese children.

Public transport

 * ETUSA (urban and suburban bus transportation for Algiers) operates bus service in Algiers and the surrounding suburbs. 54 lines are operating, with service from 5:30 a.m. to 12:45 a.m.
 * SNTF (national railroad company) operates commuter-rail lines connecting the capital to the surrounding suburbs.
 * Algiers Metro, opened November 1, 2011.
 * Algiers tramway, opened on May 8, 2011.
 * Houari Boumediene Airport is located 20 km from the city. The airport serves domestics, many European cities, West Africa, the Middle East, Asia and North America. On July 5, 2006, a new international air terminal was opened for service. The terminal is managed by Aéroports de Paris.

4 urban beltways:
 * El Madania – Belouizdad
 * Notre Dame d'Afrique – Bologhine
 * Memorial des Martyres/Riad el Feth – Jardin d'essais
 * Palais de la culture – Oued Kniss

Sports
Algiers is the sporting centre of Algeria. The city has a number of professional clubs in the variety of sports, which have won national and international titles. Among the sports facilities within the city, there is an enormous sporting complex – Complex of OCO – Mohamed Boudiaf. This includes the Stade 5 Juillet 1962 (capacity 64,000), a venue for athletics, an Olympic swimming pool, a multisports room (the Cupola), an 18-hole golf course, and several tennis courts.

The following major sporting events have been held in Algiers (not-exhaustive list):

Football clubs
Major association football club based in Algiers include:

Twin towns – sister cities
Algiers is twinned with:

 * Montreal, Canada
 * Moscow, Russia
 * Sofia, Bulgaria

In addition, many of the wards and cities within Algiers maintain sister-city relationships with other foreign cities.
 * Santiago, Chile

Cooperation agreements
Algiers has cooperation agreements with:
 * Lisbon, Portugal
 * Paris, France

Films about Algiers

 * Algiers, 1938, starring Charles Boyer and Hedy Lamarr, and directed by John Cromwell;
 * The Battle of Algiers, 1966, directed by Gillo Pontecorvo;
 * Tahya ya Didou, Alger Insolite, 1970, Mohammed Zinet;
 * Bab El-Oued City, 1994, directed by Merzak Allouache;
 * Viva Laldjérie, 2003, directed by Nadir Moknèche, with Biyouna and Lubna Azabal;
 * Bab el Web, 2004, directed by Merzak Allouache, with Samy Naceri, Julie Gayet, Faudel;
 * Once upon a time in the Oued, 2005, directed by Djamel Bensalah;
 * Beur, White, Red, 2005, directed by Mahmoud Zemmouri.
 * Delice Paloma, 2007, directed by Nadir Moknèche, with Biyouna and Nadia Kaci.
 * Abbott and Costello in the Foreign Legion, 1950, starring Bud Abbott and Lou Costello.
 * Carry on Spying 1964, directed by Gerald Thomas with Kenneth Williams, Charles Hawtrey, Barbara Windsor & Renee Houston

Notable people
• Sidi Abd al-Rahman al-Tha'alibi, 15th-century theologian and sufi.

• Sidi Ahmed Zouaoui, 15th-century theologian and sufi.

• Raphael Zeror (1681–1737), Algerian rabbi

• Sidi M'hamed Bou Qobrine, 18th-century theologian and sufi.

• Mohamed ben Zamoum, 19th-century resistant against French colonization.

• Khalid ibn Hashim, 19th-20th-century resistant against French colonization.

• Albert Camus 20th-century Nobel Laureate

• Abdelhalim Bensmaia, 20th-century scholar, reformist, humanist and musician.

• Lyès Deriche, 20th-century leader of the Algerian national political movement.

• Brahim Boushaki, 20th-century theologian and sufi.

• Ali La Pointe, 20th-century militant of the Algerian national political movement.

• Mohamed Aïchaoui, 20th-century militant of the Algerian national political movement.

• Mohamed Seghir Boushaki, 20th-century leader of the Algerian national political movement.

• El Hadj M'Hamed El Anka, 20th-century artist.

• Ahmed Mahsas, 20th-century leader of the Algerian national political movement.

• Hocine Mezali, 20th-21st-century journalist and writer.

• Djamila Bouhired, 20th-century militant of the Algerian national political movement.

• Hassiba Ben Bouali, 20th-century militant of the Algerian national political movement.

• Mohamed Belouizdad, 20th-century leader of the Algerian national political movement against the French.

• Djamila Boupacha, 20th-century militant of the Algerian national political movement.

• Mohamed Bencheneb, 20th-century professor, writer and historian.

• Mourad Didouche, 20th-century leader of the Algerian national political movement.

• Islam Slimani, footballer

• Ali Haroun, 20th-century politician and lawyer.

• Mohamed Missouri, 20th-century boxer and coach.

• Hamdan Khodja, 19th-century dignitary and scholar.

• Mohamed Belhocine, 20th-21st-century professor of internal medicine and epidemiology.

• Amine ibn El Boushaki, 20th-21st-century judoka.

• Amina Belouizdad, 20th-century television presenter.

• Ali Fawzi Rebaine, 21st-century politician and doctor.

• Mohamed Arkab, 20th-21st-century politician and engineer.

• Rezki Zerarti, 20th-21st-century politician and engineer.

• Gaston Ricci (1869–1952), French politician, born in Algiers.

• Henri Fiori (1881–1963), French politician, born in Algiers.

• Raymond Laquière (1881–1973), French politician, born in Algiers.

• Jean-Marie Guastavino (1886–1960), French politician, born in Algiers.

• Mustapha Khedali (1934–2008), Algerian football player and manager

• Alain Dorval (1946-2024), French voice actor. He dubbed Sylvester Stallone in French versions.

• Abdelatif Alouach (born 1976), freediver

• Mohamed Harrat (born 1976), footballer

• Lotfi Laggoun (born 1984 in Alger), footballer

• Lyna Khoudri (born 1992), Algerian-French actress

• Arezki Hamza Dembri (born 2004), Algerian footballer

• Tony Gatlif (born 1948), French film director

title: Algiers


text:
Ibn al-Haytham

Ḥasan Ibn al-Haytham (Latinized as Alhazen; ; full name أبو علي، الحسن بن الحسن بن الهيثم; c. 965) was a medieval mathematician, astronomer, and physicist of the Islamic Golden Age from present-day Iraq. Referred to as "the father of modern optics", he made significant contributions to the principles of optics and visual perception in particular. His most influential work is titled Kitāb al-Manāẓir (Arabic: كتاب المناظر, "Book of Optics"), written during 1011–1021, which survived in a Latin edition. : "The three most recognizable Islamic contributors to meteorology were: the Alexandrian mathematician/ astronomer Ibn al-Haytham (Alhazen 965–1039), the Arab-speaking Persian physician Ibn Sina (Avicenna 980–1037), and the Spanish Moorish physician/jurist Ibn Rushd (Averroes; 1126–1198)." He has been dubbed the "father of modern optics" by the UNESCO. . . . Specifically, he was the first to explain that vision occurs when light bounces on an object and then enters an eye. The works of Alhazen were frequently cited during the scientific revolution by Isaac Newton, Johannes Kepler, Christiaan Huygens, and Galileo Galilei.

Ibn al-Haytham was the first to correctly explain the theory of vision, and to argue that vision occurs in the brain, pointing to observations that it is subjective and affected by personal experience. He also stated the principle of least time for refraction which would later become the Fermat's principle. He made major contributions to catoptrics and dioptrics by studying reflection, refraction and nature of images formed by light rays. Ibn al-Haytham was an early proponent of the concept that a hypothesis must be supported by experiments based on confirmable procedures or mathematical reasoning—an early pioneer in the scientific method five centuries before Renaissance scientists,   he is sometimes described as the world's "first true scientist". He was also a polymath, writing on philosophy, theology and medicine.

Born in Basra, he spent most of his productive period in the Fatimid capital of Cairo and earned his living authoring various treatises and tutoring members of the nobilities. Ibn al-Haytham is sometimes given the byname al-Baṣrī after his birthplace, or al-Miṣrī ("the Egyptian"). Al-Haytham was dubbed the "Second Ptolemy" by Abu'l-Hasan Bayhaqi and "The Physicist" by John Peckham. Ibn al-Haytham paved the way for the modern science of physical optics.

Biography
Ibn al-Haytham (Alhazen) was born c. 965 to a family of Arab  or Persian     origin in Basra, Iraq, which was at the time part of the Buyid emirate. His initial influences were in the study of religion and service to the community. At the time, society had a number of conflicting views of religion that he ultimately sought to step aside from religion. This led to him delving into the study of mathematics and science. He held a position with the title of vizier in his native Basra, and became famous for his knowledge of applied mathematics, as evidenced by his attempt to regulate the flooding of the Nile.

Upon his return to Cairo, he was given an administrative post. After he proved unable to fulfill this task as well, he contracted the ire of the caliph al-Hakim, and is said to have been forced into hiding until the caliph's death in 1021, after which his confiscated possessions were returned to him. Legend has it that Alhazen feigned madness and was kept under house arrest during this period. During this time, he wrote his influential Book of Optics. Alhazen continued to live in Cairo, in the neighborhood of the famous University of al-Azhar, and lived from the proceeds of his literary production until his death in c. 1040. (A copy of Apollonius' Conics, written in Ibn al-Haytham's own handwriting exists in Aya Sofya: (MS Aya Sofya 2762, 307 fob., dated Safar 415 A.H. [1024]).)

Among his students were Sorkhab (Sohrab), a Persian from Semnan, and Abu al-Wafa Mubashir ibn Fatek, an Egyptian prince.

Book of Optics
Alhazen's most famous work is his seven-volume treatise on optics Kitab al-Manazir (Book of Optics), written from 1011 to 1021. In it, Ibn al-Haytham was the first to explain that vision occurs when light reflects from an object and then passes to one's eyes, and to argue that vision occurs in the brain, pointing to observations that it is subjective and affected by personal experience.

Optics was translated into Latin by an unknown scholar at the end of the 12th century or the beginning of the 13th century.

This work enjoyed a great reputation during the Middle Ages. The Latin version of De aspectibus was translated at the end of the 14th century into Italian vernacular, under the title De li aspecti.

It was printed by Friedrich Risner in 1572, with the title Opticae thesaurus: Alhazeni Arabis libri septem, nuncprimum editi; Eiusdem liber De Crepusculis et nubium ascensionibus (English: Treasury of Optics: seven books by the Arab Alhazen, first edition; by the same, on twilight and the height of clouds). Risner is also the author of the name variant "Alhazen"; before Risner he was known in the west as Alhacen. Works by Alhazen on geometric subjects were discovered in the Bibliothèque nationale in Paris in 1834 by E. A. Sedillot. In all, A. Mark Smith has accounted for 18 full or near-complete manuscripts, and five fragments, which are preserved in 14 locations, including one in the Bodleian Library at Oxford, and one in the library of Bruges.

Theory of optics
Two major theories on vision prevailed in classical antiquity. The first theory, the emission theory, was supported by such thinkers as Euclid and Ptolemy, who believed that sight worked by the eye emitting rays of light. The second theory, the intromission theory supported by Aristotle and his followers, had physical forms entering the eye from an object. Previous Islamic writers (such as al-Kindi) had argued essentially on Euclidean, Galenist, or Aristotelian lines. The strongest influence on the Book of Optics was from Ptolemy's Optics, while the description of the anatomy and physiology of the eye was based on Galen's account. Alhazen's achievement was to come up with a theory that successfully combined parts of the mathematical ray arguments of Euclid, the medical tradition of Galen, and the intromission theories of Aristotle. Alhazen's intromission theory followed al-Kindi (and broke with Aristotle) in asserting that "from each point of every colored body, illuminated by any light, issue light and color along every straight line that can be drawn from that point". This left him with the problem of explaining how a coherent image was formed from many independent sources of radiation; in particular, every point of an object would send rays to every point on the eye.

What Alhazen needed was for each point on an object to correspond to one point only on the eye. He attempted to resolve this by asserting that the eye would only perceive perpendicular rays from the object—for any one point on the eye, only the ray that reached it directly, without being refracted by any other part of the eye, would be perceived. He argued, using a physical analogy, that perpendicular rays were stronger than oblique rays: in the same way that a ball thrown directly at a board might break the board, whereas a ball thrown obliquely at the board would glance off, perpendicular rays were stronger than refracted rays, and it was only perpendicular rays which were perceived by the eye. As there was only one perpendicular ray that would enter the eye at any one point, and all these rays would converge on the centre of the eye in a cone, this allowed him to resolve the problem of each point on an object sending many rays to the eye; if only the perpendicular ray mattered, then he had a one-to-one correspondence and the confusion could be resolved. He later asserted (in book seven of the Optics) that other rays would be refracted through the eye and perceived as if perpendicular. His arguments regarding perpendicular rays do not clearly explain why only perpendicular rays were perceived; why would the weaker oblique rays not be perceived more weakly? His later argument that refracted rays would be perceived as if perpendicular does not seem persuasive. However, despite its weaknesses, no other theory of the time was so comprehensive, and it was enormously influential, particularly in Western Europe. Directly or indirectly, his De Aspectibus (Book of Optics) inspired much activity in optics between the 13th and 17th centuries. Kepler's later theory of the retinal image (which resolved the problem of the correspondence of points on an object and points in the eye) built directly on the conceptual framework of Alhazen.

Alhazen showed through experiment that light travels in straight lines, and carried out various experiments with lenses, mirrors, refraction, and reflection. His analyses of reflection and refraction considered the vertical and horizontal components of light rays separately.

Alhazen studied the process of sight, the structure of the eye, image formation in the eye, and the visual system. Ian P. Howard argued in a 1996 Perception article that Alhazen should be credited with many discoveries and theories previously attributed to Western Europeans writing centuries later. For example, he described what became in the 19th century Hering's law of equal innervation. He wrote a description of vertical horopters 600 years before Aguilonius that is actually closer to the modern definition than Aguilonius's—and his work on binocular disparity was repeated by Panum in 1858. Craig Aaen-Stockdale, while agreeing that Alhazen should be credited with many advances, has expressed some caution, especially when considering Alhazen in isolation from Ptolemy, with whom Alhazen was extremely familiar. Alhazen corrected a significant error of Ptolemy regarding binocular vision, but otherwise his account is very similar; Ptolemy also attempted to explain what is now called Hering's law. In general, Alhazen built on and expanded the optics of Ptolemy.

In a more detailed account of Ibn al-Haytham's contribution to the study of binocular vision based on Lejeune and Sabra, Raynaud showed that the concepts of correspondence, homonymous and crossed diplopia were in place in Ibn al-Haytham's optics. But contrary to Howard, he explained why Ibn al-Haytham did not give the circular figure of the horopter and why, by reasoning experimentally, he was in fact closer to the discovery of Panum's fusional area than that of the Vieth-Müller circle. In this regard, Ibn al-Haytham's theory of binocular vision faced two main limits: the lack of recognition of the role of the retina, and obviously the lack of an experimental investigation of ocular tracts.

Alhazen's most original contribution was that, after describing how he thought the eye was anatomically constructed, he went on to consider how this anatomy would behave functionally as an optical system. His understanding of pinhole projection from his experiments appears to have influenced his consideration of image inversion in the eye, which he sought to avoid. He maintained that the rays that fell perpendicularly on the lens (or glacial humor as he called it) were further refracted outward as they left the glacial humor and the resulting image thus passed upright into the optic nerve at the back of the eye. He followed Galen in believing that the lens was the receptive organ of sight, although some of his work hints that he thought the retina was also involved.

Alhazen's synthesis of light and vision adhered to the Aristotelian scheme, exhaustively describing the process of vision in a logical, complete fashion.

His research in catoptrics (the study of optical systems using mirrors) was centred on spherical and parabolic mirrors and spherical aberration. He made the observation that the ratio between the angle of incidence and refraction does not remain constant, and investigated the magnifying power of a lens.

Law of reflection
Alhazen was the first physicist to give complete statement of the law of reflection. He was first to state that the incident ray, the reflected ray, and the normal to the surface all lie in a same plane perpendicular to reflecting plane.

Alhazen's problem
His work on catoptrics in Book V of the Book of Optics contains a discussion of what is now known as Alhazen's problem, first formulated by Ptolemy in 150 AD. It comprises drawing lines from two points in the plane of a circle meeting at a point on the circumference and making equal angles with the normal at that point. This is equivalent to finding the point on the edge of a circular billiard table at which a player must aim a cue ball at a given point to make it bounce off the table edge and hit another ball at a second given point. Thus, its main application in optics is to solve the problem, "Given a light source and a spherical mirror, find the point on the mirror where the light will be reflected to the eye of an observer." This leads to an equation of the fourth degree. This eventually led Alhazen to derive a formula for the sum of fourth powers, where previously only the formulas for the sums of squares and cubes had been stated. His method can be readily generalized to find the formula for the sum of any integral powers, although he did not himself do this (perhaps because he only needed the fourth power to calculate the volume of the paraboloid he was interested in). He used his result on sums of integral powers to perform what would now be called an integration, where the formulas for the sums of integral squares and fourth powers allowed him to calculate the volume of a paraboloid. Alhazen eventually solved the problem using conic sections and a geometric proof. His solution was extremely long and complicated and may not have been understood by mathematicians reading him in Latin translation. Later mathematicians used Descartes' analytical methods to analyse the problem. An algebraic solution to the problem was finally found in 1965 by Jack M. Elkin, an actuarian. Other solutions were discovered in 1989, by Harald Riede and in 1997 by the Oxford mathematician Peter M. Neumann. Recently, Mitsubishi Electric Research Laboratories (MERL) researchers solved the extension of Alhazen's problem to general rotationally symmetric quadric mirrors including hyperbolic, parabolic and elliptical mirrors.

Camera Obscura
The camera obscura was known to the ancient Chinese, and was described by the Han Chinese polymath Shen Kuo in his scientific book Dream Pool Essays, published in the year 1088 C.E. Aristotle had discussed the basic principle behind it in his Problems, but Alhazen's work contained the first clear description of camera obscura. and early analysis of the device.

Ibn al-Haytham used a camera obscura mainly to observe a partial solar eclipse. In his essay, Ibn al-Haytham writes that he observed the sickle-like shape of the sun at the time of an eclipse. The introduction reads as follows: "The image of the sun at the time of the eclipse, unless it is total, demonstrates that when its light passes through a narrow, round hole and is cast on a plane opposite to the hole it takes on the form of a moonsickle."

It is admitted that his findings solidified the importance in the history of the camera obscura but this treatise is important in many other respects.

Ancient optics and medieval optics were divided into optics and burning mirrors. Optics proper mainly focused on the study of vision, while burning mirrors focused on the properties of light and luminous rays. On the shape of the eclipse is probably one of the first attempts made by Ibn al-Haytham to articulate these two sciences.

Very often Ibn al-Haytham's discoveries benefited from the intersection of mathematical and experimental contributions. This is the case with On the shape of the eclipse. Besides the fact that this treatise allowed more people to study partial eclipses of the sun, it especially allowed to better understand how the camera obscura works. This treatise is a physico-mathematical study of image formation inside the camera obscura. Ibn al-Haytham takes an experimental approach, and determines the result by varying the size and the shape of the aperture, the focal length of the camera, the shape and intensity of the light source.

In his work he explains the inversion of the image in the camera obscura, the fact that the image is similar to the source when the hole is small, but also the fact that the image can differ from the source when the hole is large. All these results are produced by using a point analysis of the image.

Refractometer
In the seventh tract of his book of optics, Alhazen described an apparatus for experimenting with various cases of refraction, in order to investigate the relations between the angle of incidence, the angle of refraction and the angle of deflection. This apparatus was a modified version of an apparatus used by Ptolemy for similar purpose.

Unconscious inference
Alhazen basically states the concept of unconscious inference in his discussion of colour before adding that the inferential step between sensing colour and differentiating it is shorter than the time taken between sensing and any other visible characteristic (aside from light), and that "time is so short as not to be clearly apparent to the beholder." Naturally, this suggests that the colour and form are perceived elsewhere. Alhazen goes on to say that information must travel to the central nerve cavity for processing and: the sentient organ does not sense the forms that reach it from the visible objects until after it has been affected by these forms; thus it does not sense color as color or light as light until after it has been affected by the form of color or light. Now the affectation received by the sentient organ from the form of color or of light is a certain change; and change must take place in time; …..and it is in the time during which the form extends from the sentient organ's surface to the cavity of the common nerve, and in (the time) following that, that the sensitive faculty, which exists in the whole of the sentient body will perceive color as color…Thus the last sentient's perception of color as such and of light as such takes place at a time following that in which the form arrives from the surface of the sentient organ to the cavity of the common nerve.

Color constancy
Alhazen explained color constancy by observing that the light reflected from an object is modified by the object's color. He explained that the quality of the light and the color of the object are mixed, and the visual system separates light and color. In Book II, Chapter 3 he writes: Again the light does not travel from the colored object to the eye unaccompanied by the color, nor does the form of the color pass from the colored object to the eye unaccompanied by the light. Neither the form of the light nor that of the color existing in the colored object can pass except as mingled together and the last sentient can only perceive them as mingled together. Nevertheless, the sentient perceives that the visible object is luminous and that the light seen in the object is other than the color and that these are two properties.

Other contributions
The Kitab al-Manazir (Book of Optics) describes several experimental observations that Alhazen made and how he used his results to explain certain optical phenomena using mechanical analogies. He conducted experiments with projectiles and concluded that only the impact of perpendicular projectiles on surfaces was forceful enough to make them penetrate, whereas surfaces tended to deflect oblique projectile strikes. For example, to explain refraction from a rare to a dense medium, he used the mechanical analogy of an iron ball thrown at a thin slate covering a wide hole in a metal sheet. A perpendicular throw breaks the slate and passes through, whereas an oblique one with equal force and from an equal distance does not. He also used this result to explain how intense, direct light hurts the eye, using a mechanical analogy: Alhazen associated 'strong' lights with perpendicular rays and 'weak' lights with oblique ones. The obvious answer to the problem of multiple rays and the eye was in the choice of the perpendicular ray, since only one such ray from each point on the surface of the object could penetrate the eye.

Sudanese psychologist Omar Khaleefa has argued that Alhazen should be considered the founder of experimental psychology, for his pioneering work on the psychology of visual perception and optical illusions. Khaleefa has also argued that Alhazen should also be considered the "founder of psychophysics", a sub-discipline and precursor to modern psychology. Although Alhazen made many subjective reports regarding vision, there is no evidence that he used quantitative psychophysical techniques and the claim has been rebuffed.

Alhazen offered an explanation of the Moon illusion, an illusion that played an important role in the scientific tradition of medieval Europe. Many authors repeated explanations that attempted to solve the problem of the Moon appearing larger near the horizon than it does when higher up in the sky. Alhazen argued against Ptolemy's refraction theory, and defined the problem in terms of perceived, rather than real, enlargement. He said that judging the distance of an object depends on there being an uninterrupted sequence of intervening bodies between the object and the observer. When the Moon is high in the sky there are no intervening objects, so the Moon appears close. The perceived size of an object of constant angular size varies with its perceived distance. Therefore, the Moon appears closer and smaller high in the sky, and further and larger on the horizon. Through works by Roger Bacon, John Pecham and Witelo based on Alhazen's explanation, the Moon illusion gradually came to be accepted as a psychological phenomenon, with the refraction theory being rejected in the 17th century. Although Alhazen is often credited with the perceived distance explanation, he was not the first author to offer it. Cleomedes (c. 2nd century) gave this account (in addition to refraction), and he credited it to Posidonius (c.  135–50 BCE). Ptolemy may also have offered this explanation in his Optics, but the text is obscure. Alhazen's writings were more widely available in the Middle Ages than those of these earlier authors, and that probably explains why Alhazen received the credit.

Scientific method
"Therefore, the seeker after the truth is not one who studies the writings of the ancients and, following his natural disposition, puts his trust in them, but rather the one who suspects his faith in them and questions what he gathers from them, the one who submits to argument and demonstration, and not to the sayings of a human being whose nature is fraught with all kinds of imperfection and deficiency. The duty of the man who investigates the writings of scientists, if learning the truth is his goal, is to make himself an enemy of all that he reads, and ... attack it from every side. He should also suspect himself as he performs his critical examination of it, so that he may avoid falling into either prejudice or leniency." An aspect associated with Alhazen's optical research is related to systemic and methodological reliance on experimentation (i'tibar)(Arabic: اختبار) and controlled testing in his scientific inquiries. Moreover, his experimental directives rested on combining classical physics (ilm tabi'i) with mathematics (ta'alim; geometry in particular). This mathematical-physical approach to experimental science supported most of his propositions in Kitab al-Manazir (The Optics; De aspectibus or Perspectivae) and grounded his theories of vision, light and colour, as well as his research in catoptrics and dioptrics (the study of the reflection and refraction of light, respectively).

According to Matthias Schramm, Alhazen "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." G. J. Toomer expressed some skepticism regarding Schramm's view, partly because at the time (1964) the Book of Optics had not yet been fully translated from Arabic, and Toomer was concerned that without context, specific passages might be read anachronistically. While acknowledging Alhazen's importance in developing experimental techniques, Toomer argued that Alhazen should not be considered in isolation from other Islamic and ancient thinkers. Toomer concluded his review by saying that it would not be possible to assess Schramm's claim that Ibn al-Haytham was the true founder of modern physics without translating more of Alhazen's work and fully investigating his influence on later medieval writers.

Optical treatises
Besides the Book of Optics, Alhazen wrote several other treatises on the same subject, including his Risala fi l-Daw' (Treatise on Light). He investigated the properties of luminance, the rainbow, eclipses, twilight, and moonlight. Experiments with mirrors and the refractive interfaces between air, water, and glass cubes, hemispheres, and quarter-spheres provided the foundation for his theories on catoptrics.

Celestial physics
Alhazen discussed the physics of the celestial region in his Epitome of Astronomy, arguing that Ptolemaic models must be understood in terms of physical objects rather than abstract hypotheses—in other words that it should be possible to create physical models where (for example) none of the celestial bodies would collide with each other. The suggestion of mechanical models for the Earth centred Ptolemaic model "greatly contributed to the eventual triumph of the Ptolemaic system among the Christians of the West". Alhazen's determination to root astronomy in the realm of physical objects was important, however, because it meant astronomical hypotheses "were accountable to the laws of physics", and could be criticised and improved upon in those terms.

He also wrote Maqala fi daw al-qamar (On the Light of the Moon).

Mechanics
In his work, Alhazen discussed theories on the motion of a body.

On the Configuration of the World
In his On the Configuration of the World Alhazen presented a detailed description of the physical structure of the earth:"The earth as a whole is a round sphere whose center is the center of the world. It is stationary in its [the world's] middle, fixed in it and not moving in any direction nor moving with any of the varieties of motion, but always at rest."

The book is a non-technical explanation of Ptolemy's Almagest, which was eventually translated into Hebrew and Latin in the 13th and 14th centuries and subsequently had an influence on astronomers such as Georg von Peuerbach during the European Middle Ages and Renaissance.

Doubts Concerning Ptolemy
In his Al-Shukūk ‛alā Batlamyūs, variously translated as Doubts Concerning Ptolemy or Aporias against Ptolemy, published at some time between 1025 and 1028, Alhazen criticized Ptolemy's Almagest, Planetary Hypotheses, and Optics, pointing out various contradictions he found in these works, particularly in astronomy. Ptolemy's Almagest concerned mathematical theories regarding the motion of the planets, whereas the Hypotheses concerned what Ptolemy thought was the actual configuration of the planets. Ptolemy himself acknowledged that his theories and configurations did not always agree with each other, arguing that this was not a problem provided it did not result in noticeable error, but Alhazen was particularly scathing in his criticism of the inherent contradictions in Ptolemy's works. He considered that some of the mathematical devices Ptolemy introduced into astronomy, especially the equant, failed to satisfy the physical requirement of uniform circular motion, and noted the absurdity of relating actual physical motions to imaginary mathematical points, lines and circles:

"Ptolemy assumed an arrangement (hay'a) that cannot exist, and the fact that this arrangement produces in his imagination the motions that belong to the planets does not free him from the error he committed in his assumed arrangement, for the existing motions of the planets cannot be the result of an arrangement that is impossible to exist... [F]or a man to imagine a circle in the heavens, and to imagine the planet moving in it does not bring about the planet's motion."

Having pointed out the problems, Alhazen appears to have intended to resolve the contradictions he pointed out in Ptolemy in a later work. Alhazen believed there was a "true configuration" of the planets that Ptolemy had failed to grasp. He intended to complete and repair Ptolemy's system, not to replace it completely. In the Doubts Concerning Ptolemy Alhazen set out his views on the difficulty of attaining scientific knowledge and the need to question existing authorities and theories:

"Truth is sought for itself [but] the truths, [he warns] are immersed in uncertainties [and the scientific authorities (such as Ptolemy, whom he greatly respected) are] not immune from error..."

He held that the criticism of existing theories—which dominated this book—holds a special place in the growth of scientific knowledge.

Model of the Motions of Each of the Seven Planets
Alhazen's The Model of the Motions of Each of the Seven Planets was written c. 1038. Only one damaged manuscript has been found, with only the introduction and the first section, on the theory of planetary motion, surviving. (There was also a second section on astronomical calculation, and a third section, on astronomical instruments.) Following on from his Doubts on Ptolemy, Alhazen described a new, geometry-based planetary model, describing the motions of the planets in terms of spherical geometry, infinitesimal geometry and trigonometry. He kept a geocentric universe and assumed that celestial motions are uniformly circular, which required the inclusion of epicycles to explain observed motion, but he managed to eliminate Ptolemy's equant. In general, his model didn't try to provide a causal explanation of the motions, but concentrated on providing a complete, geometric description that could explain observed motions without the contradictions inherent in Ptolemy's model.

Other astronomical works
Alhazen wrote a total of twenty-five astronomical works, some concerning technical issues such as Exact Determination of the Meridian, a second group concerning accurate astronomical observation, a third group concerning various astronomical problems and questions such as the location of the Milky Way; Alhazen made the first systematic effort of evaluating the Milky Way's parallax, combining Ptolemy's data and his own. He concluded that the parallax is (probably very much) smaller than Lunar parallax, and the Milky way should be a celestial object. Though he was not the first who argued that the Milky Way does not belong to the atmosphere, he is the first who did quantitative analysis for the claim. The fourth group consists of ten works on astronomical theory, including the Doubts and Model of the Motions discussed above.

Mathematical works
In mathematics, Alhazen built on the mathematical works of Euclid and Thabit ibn Qurra and worked on "the beginnings of the link between algebra and geometry". Alhazen made developments in conic sections and number theory.

He developed a formula for summing the first 100 natural numbers, using a geometric proof to prove the formula.

Geometry
Alhazen explored what is now known as the Euclidean parallel postulate, the fifth postulate in Euclid's Elements, using a proof by contradiction, and in effect introducing the concept of motion into geometry. He formulated the Lambert quadrilateral, which Boris Abramovich Rozenfeld names the "Ibn al-Haytham–Lambert quadrilateral". He was criticised by Omar Khayyam who pointed that Aristotle had condemned the use of motion in geometry.

In elementary geometry, Alhazen attempted to solve the problem of squaring the circle using the area of lunes (crescent shapes), but later gave up on the impossible task. The two lunes formed from a right triangle by erecting a semicircle on each of the triangle's sides, inward for the hypotenuse and outward for the other two sides, are known as the lunes of Alhazen; they have the same total area as the triangle itself.

Number theory
Alhazen's contributions to number theory include his work on perfect numbers. In his Analysis and Synthesis, he may have been the first to state that every even perfect number is of the form 2n−1(2n − 1) where 2n − 1 is prime, but he was not able to prove this result; Euler later proved it in the 18th century, and it is now called the Euclid–Euler theorem.

Alhazen solved problems involving congruences using what is now called Wilson's theorem. In his Opuscula, Alhazen considers the solution of a system of congruences, and gives two general methods of solution. His first method, the canonical method, involved Wilson's theorem, while his second method involved a version of the Chinese remainder theorem.

Calculus
Alhazen discovered the sum formula for the fourth power, using a method that could be generally used to determine the sum for any integral power. He used this to find the volume of a paraboloid. He could find the integral formula for any polynomial without having developed a general formula.

Influence of Melodies on the Souls of Animals
Alhazen also wrote a Treatise on the Influence of Melodies on the Souls of Animals, although no copies have survived. It appears to have been concerned with the question of whether animals could react to music, for example whether a camel would increase or decrease its pace.

Engineering
In engineering, one account of his career as a civil engineer has him summoned to Egypt by the Fatimid Caliph, Al-Hakim bi-Amr Allah, to regulate the flooding of the Nile River. He carried out a detailed scientific study of the annual inundation of the Nile River, and he drew plans for building a dam, at the site of the modern-day Aswan Dam. His field work, however, later made him aware of the impracticality of this scheme, and he soon feigned madness so he could avoid punishment from the Caliph.

Philosophy
In his Treatise on Place, Alhazen disagreed with Aristotle's view that nature abhors a void, and he used geometry in an attempt to demonstrate that place (al-makan) is the imagined three-dimensional void between the inner surfaces of a containing body. Abd-el-latif, a supporter of Aristotle's philosophical view of place, later criticized the work in Fi al-Radd 'ala Ibn al-Haytham fi al-makan (A refutation of Ibn al-Haytham's place) for its geometrization of place.

Alhazen also discussed space perception and its epistemological implications in his Book of Optics. In "tying the visual perception of space to prior bodily experience, Alhazen unequivocally rejected the intuitiveness of spatial perception and, therefore, the autonomy of vision. Without tangible notions of distance and size for correlation, sight can tell us next to nothing about such things."

Theology
Alhazen was a Muslim and most sources report that he was a Sunni and a follower of the Ash'ari school. Ziauddin Sardar says that some of the greatest Muslim scientists, such as Ibn al-Haytham and Abū Rayhān al-Bīrūnī, who were pioneers of the scientific method, were themselves followers of the Ashʿari school of Islamic theology. Like other Ashʿarites who believed that faith or taqlid should apply only to Islam and not to any ancient Hellenistic authorities, Ibn al-Haytham's view that taqlid should apply only to prophets of Islam and not to any other authorities formed the basis for much of his scientific skepticism and criticism against Ptolemy and other ancient authorities in his Doubts Concerning Ptolemy and Book of Optics.

Alhazen wrote a work on Islamic theology in which he discussed prophethood and developed a system of philosophical criteria to discern its false claimants in his time. He also wrote a treatise entitled Finding the Direction of Qibla by Calculation in which he discussed finding the Qibla, where prayers (salat) are directed towards, mathematically.

There are occasional references to theology or religious sentiment in his technical works, e.g. in Doubts Concerning Ptolemy: "Truth is sought for its own sake ... Finding the truth is difficult, and the road to it is rough. For the truths are plunged in obscurity. ... God, however, has not preserved the scientist from error and has not safeguarded science from shortcomings and faults. If this had been the case, scientists would not have disagreed upon any point of science..." In The Winding Motion: "From the statements made by the noble Shaykh, it is clear that he believes in Ptolemy's words in everything he says, without relying on a demonstration or calling on a proof, but by pure imitation (taqlid); that is how experts in the prophetic tradition have faith in Prophets, may the blessing of God be upon them. But it is not the way that mathematicians have faith in specialists in the demonstrative sciences."

Regarding the relation of objective truth and God: "I constantly sought knowledge and truth, and it became my belief that for gaining access to the effulgence and closeness to God, there is no better way than that of searching for truth and knowledge."

Legacy
Alhazen made significant contributions to optics, number theory, geometry, astronomy and natural philosophy. Alhazen's work on optics is credited with contributing a new emphasis on experiment.

His main work, Kitab al-Manazir (Book of Optics), was known in the Muslim world mainly, but not exclusively, through the thirteenth-century commentary by Kamāl al-Dīn al-Fārisī, the Tanqīḥ al-Manāẓir li-dhawī l-abṣār wa l-baṣā'ir. In al-Andalus, it was used by the eleventh-century prince of the Banu Hud dynasty of Zaragossa and author of an important mathematical text, al-Mu'taman ibn Hūd. A Latin translation of the Kitab al-Manazir was made probably in the late twelfth or early thirteenth century. This translation was read by and greatly influenced a number of scholars in Christian Europe including: Roger Bacon, Robert Grosseteste, Witelo, Giambattista della Porta, Leonardo da Vinci, Galileo Galilei, Christiaan Huygens, René Descartes, and Johannes Kepler. Meanwhile, in the Islamic world, Alhazen's work influenced Averroes' writings on optics, and his legacy was further advanced through the 'reforming' of his Optics by Persian scientist Kamal al-Din al-Farisi (died c. 1320) in the latter's Kitab Tanqih al-Manazir (The Revision of [Ibn al-Haytham's] Optics). Alhazen wrote as many as 200 books, although only 55 have survived. Some of his treatises on optics survived only through Latin translation. During the Middle Ages his books on cosmology were translated into Latin, Hebrew and other languages.

H. J. J. Winter, a British historian of science, summing up the importance of Ibn al-Haytham in the history of physics wrote: "After the death of Archimedes no really great physicist appeared until Ibn al-Haytham. If, therefore, we confine our interest only to the history of physics, there is a long period of over twelve hundred years during which the Golden Age of Greece gave way to the era of Muslim Scholasticism, and the experimental spirit of the noblest physicist of Antiquity lived again in the Arab Scholar from Basra."

Although only one commentary on Alhazen's optics has survived the Islamic Middle Ages, Geoffrey Chaucer mentions the work in The Canterbury Tales: "They spoke of Alhazen and Vitello, And Aristotle, who wrote, in their lives, On strange mirrors and optical instruments."

The impact crater Alhazen on the Moon is named in his honour, as was the asteroid 59239 Alhazen. In honour of Alhazen, the Aga Khan University (Pakistan) named its Ophthalmology endowed chair as "The Ibn-e-Haitham Associate Professor and Chief of Ophthalmology".

The 2015 International Year of Light celebrated the 1000th anniversary of the works on optics by Ibn Al-Haytham.

In 2014, the "Hiding in the Light" episode of Cosmos: A Spacetime Odyssey, presented by Neil deGrasse Tyson, focused on the accomplishments of Ibn al-Haytham. He was voiced by Alfred Molina in the episode.

Over forty years previously, Jacob Bronowski presented Alhazen's work in a similar television documentary (and the corresponding book), The Ascent of Man. In episode 5 (The Music of the Spheres), Bronowski remarked that in his view, Alhazen was "the one really original scientific mind that Arab culture produced", whose theory of optics was not improved on till the time of Newton and Leibniz.

UNESCO declared 2015 the International Year of Light and its Director-General Irina Bokova dubbed Ibn al-Haytham 'the father of optics'. Amongst others, this was to celebrate Ibn Al-Haytham's achievements in optics, mathematics and astronomy. An international campaign, created by the 1001 Inventions organisation, titled 1001 Inventions and the World of Ibn Al-Haytham featuring a series of interactive exhibits, workshops and live shows about his work, partnering with science centers, science festivals, museums, and educational institutions, as well as digital and social media platforms. The campaign also produced and released the short educational film 1001 Inventions and the World of Ibn Al-Haytham.

Ibn al-Haytham appears on the 10,000 dinar banknote of the Iraqi dinar, series 2003.

List of works
According to medieval biographers, Alhazen wrote more than 200 works on a wide range of subjects, of which at least 96 of his scientific works are known. Most of his works are now lost, but more than 50 of them have survived to some extent. Nearly half of his surviving works are on mathematics, 23 of them are on astronomy, and 14 of them are on optics, with a few on other subjects. Not all his surviving works have yet been studied, but some of the ones that have are given below.

 * 1) Book of Optics (كتاب المناظر)
 * 2) Analysis and Synthesis (مقالة في التحليل والتركيب)
 * 3) Balance of Wisdom (ميزان الحكمة)
 * 4) Corrections to the Almagest (تصويبات على المجسطي)
 * 5) Discourse on Place (مقالة في المكان)
 * 6) Exact Determination of the Pole (التحديد الدقيق للقطب)
 * 7) Exact Determination of the Meridian (رسالة في الشفق)
 * 8) Finding the Direction of Qibla by Calculation (كيفية حساب اتجاه القبلة)
 * 9) Horizontal Sundials (المزولة الأفقية)
 * 10) Hour Lines (خطوط الساعة)
 * 11) Doubts Concerning Ptolemy (شكوك على بطليموس)
 * 12) Maqala fi'l-Qarastun (مقالة في قرسطون)
 * 13) On Completion of the Conics (إكمال المخاريط)
 * 14) On Seeing the Stars (رؤية الكواكب)
 * 15) On Squaring the Circle (مقالة فی تربیع الدائرة)
 * 16) On the Burning Sphere (المرايا المحرقة بالدوائر)
 * 17) On the Configuration of the World (تكوين العالم)
 * 18) On the Form of Eclipse (مقالة فی صورة الکسوف)
 * 19) On the Light of Stars (مقالة في ضوء النجوم)
 * 20) On the Light of the Moon (مقالة في ضوء القمر)
 * 21) On the Milky Way (مقالة في درب التبانة)
 * 22) On the Nature of Shadows (كيفيات الإظلال)
 * 23) On the Rainbow and Halo (مقالة في قوس قزح)
 * 24) Opuscula (Minor Works)
 * 25) Resolution of Doubts Concerning the Almagest (تحليل شكوك حول الجست)
 * 26) Resolution of Doubts Concerning the Winding Motion
 * 27) The Correction of the Operations in Astronomy (تصحيح العمليات في الفلك)
 * 28) The Different Heights of the Planets (اختلاف ارتفاع الكواكب)
 * 29) The Direction of Mecca (اتجاه القبلة)
 * 30) The Model of the Motions of Each of the Seven Planets (نماذج حركات الكواكب السبعة)
 * 31) The Model of the Universe (نموذج الكون)
 * 32) The Motion of the Moon (حركة القمر)
 * 33) The Ratios of Hourly Arcs to their Heights
 * 34) The Winding Motion (الحركة المتعرجة)
 * 35) Treatise on Light (رسالة في الضوء)
 * 36) Treatise on Place (رسالة في المكان)
 * 37) Treatise on the Influence of Melodies on the Souls of Animals (تأثير اللحون الموسيقية في النفوس الحيوانية)
 * 38)  كتاب في تحليل المسائل الهندسية (A book in engineering analysis)
 * 39)  الجامع في أصول الحساب (The whole in the assets of the account)
 * 40)  قول فی مساحة الکرة (Say in the sphere)
 * 41)  القول المعروف بالغریب فی حساب المعاملات (Saying the unknown in the calculation of transactions)
 * 42)  خواص المثلث من جهة العمود (Triangle properties from the side of the column)
 * 43)  رسالة فی مساحة المسجم المکافی (A message in the free space)
 * 44)  شرح أصول إقليدس (Explain the origins of Euclid)
 * 45)  المرايا المحرقة بالقطوع (The burning mirrors of the rainbow)
 * 46) مقالة في القرصتن (Treatise on Centers of Gravity)

Lost works

 * 1) A Book in which I have Summarized the Science of Optics from the Two Books of Euclid and Ptolemy, to which I have added the Notions of the First Discourse which is Missing from Ptolemy's Book
 * 2) Treatise on Burning Mirrors
 * 3) Treatise on the Nature of [the Organ of] Sight and on How Vision is Achieved Through It

Primary

 * 2 vols:   . (Philadelphia: American Philosophical Society), 2006 – 95(#2) Books 4–5 Vol 1 Commentary and Latin text  via JSTOR ; 95(#3) Vol 2 English translation, Notes, Bibl.  via JSTOR
 * Smith, A. Mark, ed. and trans. (2008) Alhacen on Image-formation and distortion in mirrors : a critical edition, with English translation and commentary, of Book 6 of Alhacen's De aspectibus, [the Medieval Latin version of Ibn al-Haytham's Kitāb al-Manāzir], Transactions of the American Philosophical Society, 2 vols: Vol 1 98(#1, section 1 –  Vol 1 Commentary and Latin text);  98(#1, section 2 – Vol 2 English translation). (Philadelphia: American Philosophical Society), 2008. Book 6 (2008)   Vol 1 Commentary and Latin text via JSTOR ; Vol 2 English translation, Notes, Bibl.  via JSTOR
 * Smith, A. Mark, ed. and trans. (2010) Alhacen on Refraction : a critical edition, with English translation and commentary, of Book 7 of Alhacen's De aspectibus, [the Medieval Latin version of Ibn al-Haytham's Kitāb al-Manāzir], Transactions of the American Philosophical Society, 2 vols: 100(#3, section 1 –  Vol 1, Introduction and Latin text); 100(#3, section 2 –  Vol 2 English translation).  (Philadelphia: American Philosophical Society), 2010.  Book 7 (2010) Vol 1 Commentary and Latin text via JSTOR ;Vol 2 English translation, Notes, Bibl.  via JSTOR
 * Smith, A. Mark, ed. and trans. (2008) Alhacen on Image-formation and distortion in mirrors : a critical edition, with English translation and commentary, of Book 6 of Alhacen's De aspectibus, [the Medieval Latin version of Ibn al-Haytham's Kitāb al-Manāzir], Transactions of the American Philosophical Society, 2 vols: Vol 1 98(#1, section 1 –  Vol 1 Commentary and Latin text);  98(#1, section 2 – Vol 2 English translation). (Philadelphia: American Philosophical Society), 2008. Book 6 (2008)   Vol 1 Commentary and Latin text via JSTOR ; Vol 2 English translation, Notes, Bibl.  via JSTOR
 * Smith, A. Mark, ed. and trans. (2010) Alhacen on Refraction : a critical edition, with English translation and commentary, of Book 7 of Alhacen's De aspectibus, [the Medieval Latin version of Ibn al-Haytham's Kitāb al-Manāzir], Transactions of the American Philosophical Society, 2 vols: 100(#3, section 1 –  Vol 1, Introduction and Latin text); 100(#3, section 2 –  Vol 2 English translation).  (Philadelphia: American Philosophical Society), 2010.  Book 7 (2010) Vol 1 Commentary and Latin text via JSTOR ;Vol 2 English translation, Notes, Bibl.  via JSTOR

Secondary

 * Belting, Hans, Afterthoughts on Alhazen's Visual Theory and Its Presence in the Pictorial Theory of Western Perspective, in: Variantology 4. On Deep Time Relations of Arts, Sciences and Technologies in the Arabic-Islamic World and Beyond, ed. by Siegfried Zielinski and Eckhard Fürlus in cooperation with Daniel Irrgang and Franziska Latell (Cologne: Verlag der Buchhandlung Walther König, 2010), pp. 19–42.
 * Graham, Mark. How Islam Created the Modern World. Amana Publications, 2006.
 * Roshdi Rashed, Optics and Mathematics: Research on the history of scientific thought in Arabic, Variorum reprints, Aldershot, 1992.
 * Roshdi Rashed, Geometry and Dioptrics the tenth century: Ibn Sahl al-Quhi and Ibn al-Haytham (in French), Les Belles Lettres, Paris, 1993
 * Roshdi Rashed, Infinitesimal Mathematics, vols. 1–5, al-Furqan Islamic Heritage Foundation, London, 1993–2006
 * Siegfried Zielinski & Franziska Latell, How One Sees, in: Variantology 4. On Deep Time Relations of Arts, Sciences and Technologies in the Arabic-Islamic World and Beyond, ed. by Siegfried Zielinski and Eckhard Fürlus in cooperation with Daniel Irrgang and Franziska Latell (Cologne: Verlag der Buchhandlung Walther König, 2010), pp. 19–42. Buchhandlung Walther-König - KWB 45: Variantology 4
 * Roshdi Rashed, Optics and Mathematics: Research on the history of scientific thought in Arabic, Variorum reprints, Aldershot, 1992.
 * Roshdi Rashed, Geometry and Dioptrics the tenth century: Ibn Sahl al-Quhi and Ibn al-Haytham (in French), Les Belles Lettres, Paris, 1993
 * Roshdi Rashed, Infinitesimal Mathematics, vols. 1–5, al-Furqan Islamic Heritage Foundation, London, 1993–2006
 * Siegfried Zielinski & Franziska Latell, How One Sees, in: Variantology 4. On Deep Time Relations of Arts, Sciences and Technologies in the Arabic-Islamic World and Beyond, ed. by Siegfried Zielinski and Eckhard Fürlus in cooperation with Daniel Irrgang and Franziska Latell (Cologne: Verlag der Buchhandlung Walther König, 2010), pp. 19–42. Buchhandlung Walther-König - KWB 45: Variantology 4
 * Siegfried Zielinski & Franziska Latell, How One Sees, in: Variantology 4. On Deep Time Relations of Arts, Sciences and Technologies in the Arabic-Islamic World and Beyond, ed. by Siegfried Zielinski and Eckhard Fürlus in cooperation with Daniel Irrgang and Franziska Latell (Cologne: Verlag der Buchhandlung Walther König, 2010), pp. 19–42. Buchhandlung Walther-König - KWB 45: Variantology 4
 * Siegfried Zielinski & Franziska Latell, How One Sees, in: Variantology 4. On Deep Time Relations of Arts, Sciences and Technologies in the Arabic-Islamic World and Beyond, ed. by Siegfried Zielinski and Eckhard Fürlus in cooperation with Daniel Irrgang and Franziska Latell (Cologne: Verlag der Buchhandlung Walther König, 2010), pp. 19–42. Buchhandlung Walther-König - KWB 45: Variantology 4

title: Ibn al-Haytham