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Bari

Bari (, ; Bare ; ) is the capital city of the Metropolitan City of Bari and of the Apulia region, on the Adriatic Sea, southern Italy. It is the second most important economic centre of mainland Southern Italy after Naples. It is a port and university city, as well as the city of Saint Nicholas. The city itself has a population of 315,284 inhabitants, and an area of over 116 km2, while the urban area has 750,000 inhabitants. The metropolitan area has 1.3 million inhabitants.

Bari is made up of four different urban sections. To the north is the closely built old town on the peninsula between two modern harbours, with the Basilica of Saint Nicholas, the Cathedral of San Sabino (1035–1171) and the Norman-Swabian Castle, which is now also a major nightlife district. To the south is the Murat quarter (erected by Joachim Murat), the modern heart of the city, which is laid out on a rectangular grid-plan with a promenade on the sea and the major shopping district (the via Sparano and via Argiro).

Modern residential zones surrounding the centre of Bari were built during the 1960s and 1970s replacing the old suburbs that had developed along roads splaying outwards from gates in the city walls. In addition, the outer suburbs developed rapidly during the 1990s.

Ancient
Bari itself known in antiquity as Barium, was a harbour of the Iapygian Peuceti. The authors of the Etymologicum Magnum have preserved an etymology by authors of antiquity about Barium, which they explain as the word "house" in Messapic. The city had strong Greek influences before the Roman era. In ancient Greek, it was known as Βάριον. In the 3rd century BC, it became part of the Roman Republic and was subsequently Romanized. The city developed strategic significance as the point of junction between the coast road and the Via Traiana and as a port for eastward trade; a branch road to Tarentum led from Barium. Its harbour, mentioned as early as 181 BC, was probably the principal one of the districts in ancient times, as it is at present, and was the centre of a fishery. The first historical bishop of Bari was Gervasius who was noted at the Council of Sardica in 347.

Middle Ages
With the fall of the Western Roman Empire in 476, it was invaded by Barbarians and occupied by the Ostrogoths. It was taken from them by the Byzantine Empire during the Gothic wars and disputed for the following two centuries with the Lombards of the Duchy of Benevento, who made it a steward.

Throughout this period, and indeed throughout the Middle Ages, Bari served as one of the major slave depots of the Mediterranean, providing a central location for the trade in Slavic slaves. The slaves were mostly captured by Venice from Dalmatia, by the Holy Roman Empire from what is now Eastern Germany and Poland, and by the Byzantines from elsewhere in the Balkans, and were generally destined for other parts of the Byzantine Empire and (most frequently) the Muslim states surrounding the Mediterranean: the Abbasid Caliphate, the Umayyad Caliphate of Córdoba, the Emirate of Sicily, and the Fatimid Caliphate (which relied on Slavs purchased at the Bari market for its legions of Sakalaba Mamluks).

For 20 years, Bari was the centre of the Emirate of Bari; the city was captured by its first emirs Kalfun in 847, who had been part of the mercenary garrison installed there by Radelchis I of Benevento. The city was conquered and the emirate extinguished in 871 following five-year campaign by Frankish Emperor Louis II, assisted by a Byzantine fleet. Chris Wickham states Louis spent five years campaigning to reduce then occupy Bari, "and then only to a Byzantine/Slav naval blockade"; "Louis took the credit" for the success, adding "at least in Frankish eyes", then concludes by noting that by remaining in southern Italy long after this success, he "achieved the near-impossible: an alliance against him of the Beneventans, Salernitans, Neapolitans and Spoletans; later sources include Sawadān as well." In 885, Bari became the residence of the local Byzantine catapan, or governor. The failed revolt (1009–1011) of the Lombard nobles Melus of Bari and his brother-in-law Dattus, against the Byzantine governorate, though it was firmly repressed at the Battle of Cannae (1018), offered their Norman adventurer allies a first foothold in the region. In 1025, under the Archbishop Byzantius, Bari became attached to the see of Rome and was granted "provincial" status.

In 1071, Bari was captured by Robert Guiscard, following a three-year siege, ending what remained of the Byzantine power in the region.

In 1095, Peter the Hermit preached the first crusade there. In October 1098, Urban II, who had consecrated the Basilica in 1089, convened the Council of Bari, one of a series of synods convoked with the intention of reconciling the Eastern and Western Church on the question of the filioque clause in the Creed, which Anselm ably defended, seated at the pope's side.

Early modern period

A long period of decline characterized the city under the dominations of Aldoino Filangieri di Candida, and those of the Kings of Naples, which held the control of the entire mainland Southern Italy from 1282 to 1806. This decline was interrupted, however, by the splendor under the Sforzas, first with the dukes Ludovico and Beatrice d'Este, then with the duchesses Isabella of Aragon and Bona Sforza. Bari also underwent Venetian domination, which led to the expansion of the port and a very prosperous period, also favored by the trade of inland products, which were in great demand on foreign markets.

In 1556, Princess Bona Sforza of Aragon, second wife of the King of Poland Sigismund I, left Poland and settled in Bari, whose principality she had inherited from her parents. During her reign, she fortified the city's castle, as evidenced by an inscription in bronze letters on the cornice around the courtyard, as well as building several churches, a monastery, two water cisterns and made many donations to the monks of the Basilica of San Nicola. Bona Sforza died in the city in 1557. Following her death, the city of Bari came under the direct rule of the kings of Naples.

In 1813, Joachim Murat, King of Naples in the Napoleonic era, began a new urbanization, changing the face of the city and setting a new "chessboard" growth model, which continued for many years to come. The village built at the time on the outskirts of the old city still retains its name.

Modern plumbing arrived in the city of Bari on 24 April 1915: it was the first cry of the Apulian Aqueduct. During the 1930s, Araldo di Crollalanza, the mayor and minister of Bari, oversaw the development of its modern waterfront.

World War II
On 11 September 1943, in connection with the Armistice of Cassibile, Bari was taken without resistance by the British 1st Airborne Division, then during October and November 1943, New Zealand troops from the 2nd New Zealand Division assembled in Bari.

The Balkan Air Force supporting the Yugoslav partisans was based at Bari.

The 1943 chemical warfare disaster
Through a tragic coincidence intended by neither of the opposing sides in World War II, Bari gained the unwelcome distinction of being the only European city in the course of that war to experience effects like those of chemical warfare.

On the night of 2 December 1943, 105 German Junkers Ju 88 bombers attacked the port of Bari, which was a key supply centre for Allied forces fighting their way up the Italian Peninsula. Over 20 Allied ships were sunk in the overcrowded harbour, including the U.S. Liberty ship John Harvey, which was carrying mustard gas; mustard gas was also reported to have been stacked on the quayside awaiting transport (the chemical agent was intended for retaliation if German forces had initiated chemical warfare). The presence of the gas was highly classified and the U.S. had not informed the British military authorities in the city of its existence. This increased the number of fatalities, since British physicians—who had no idea that they were dealing with the effects of mustard gas—prescribed treatment proper for those suffering from exposure and immersion, which proved fatal in many cases. Because rescuers were unaware they were dealing with gas casualties, many additional casualties were caused among the rescuers, through contact with the contaminated skin and clothing of those more directly exposed to the gas.

Following the attack, the harbor was closed for operations for three weeks and it did not return to full capacity until February 1944.

A member of U.S. General Dwight D. Eisenhower's medical staff, Stewart F. Alexander, was dispatched to Bari following the raid. Alexander had trained at the Army's Edgewood Arsenal in Maryland, and was familiar with some of the effects of mustard gas. Although he was not informed of the cargo carried by the John Harvey, and most victims suffered atypical symptoms caused by exposure to mustard diluted in water and oil (as opposed to airborne), Alexander rapidly concluded that mustard gas was present. Although he could not get any acknowledgement of this from the chain of command, Alexander convinced medical staffs to treat patients for mustard exposure and saved many lives as a result. He also preserved many tissue samples from autopsied victims at Bari. After World War II, these samples would result in the development of an early form of chemotherapy based on mustard, Mustine.

On the orders of Allied leaders Franklin D. Roosevelt, Winston Churchill, and Eisenhower, records were destroyed and the whole affair was kept secret for many years after the war. The U.S. records of the attack were declassified in 1959, but the episode remained obscure until 1967, when writer Glenn B. Infield exposed the story in his book Disaster at Bari. Additionally, there is considerable dispute as to the exact number of fatalities. In one account: "[S]ixty-nine deaths were attributed in whole or in part to the mustard gas, most of them American merchant seamen". Others put the count as high as "more than one thousand Allied servicemen and more than one thousand Italian civilians".

Part of the confusion and controversy derives from the fact that the German attack, which became nicknamed "The Little Pearl Harbor" after the Japanese air attack on the American naval base in Hawaii, was highly destructive in itself, apart from the effects of the gas. Attribution of the causes of death to the gas, as distinct from the direct effects of the German attack, has proved far from easy.

The affair is the subject of two books: the aforementioned Disaster at Bari, by Glenn B. Infield, and Nightmare in Bari: The World War II Liberty Ship Poison Gas Disaster and Coverup, by Gerald Reminick.

In 1988, through the efforts of Nick T. Spark, U.S. Senators Dennis DeConcini and Bill Bradley, Stewart Alexander received recognition from the Surgeon General of the United States Army for his actions during the Bari disaster.

Charles Henderson explosion
The port of Bari was again struck by disaster on 9 April 1945 when the Liberty ship Charles Henderson exploded in the harbour while offloading 2,000 tons of aerial bombs (half of that amount had been offloaded when the explosion occurred). Three hundred and sixty people were killed and 1,730 were wounded. The harbour was again rendered non-operational, this time for a month.

Geography
Bari is the largest urban and metro area on the Adriatic. It is located in Southern Italy, at a more northerly latitude than Naples, further south than Rome.

Climate
Bari has a hot-summer Mediterranean climate (Köppen: Csa) bordering on a humid subtropical climate (Köppen: Cfa) with mild winters and hot, dry summers.

Quarters

Bari is divided into five municipalities (Municipi), constituted in 2014. The municipality is also divided into 17 official neighbourhoods ("quartieri").

Architectural landmarks

 * Teatro Margherita.
 * Teatro Piccinni.
 * Orto Botanico dell'Università di Bari, a botanical garden.
 * Santa Chiara, once church of the Teutonic Knights (as Santa maria degli Alemanni) and now houses a museum. It was restored in 1539.
 * The Acquedotto Pugliese
 * The medieval church of San Marco dei Veneziani, with a rose window in the façade.
 * Conservatory of Bari
 * San Giorgio degli Armeni.
 * Santa Teresa dei Maschi, the main Baroque church in the city (1690–1696).
 * Pane e Pomodoro Beach is the main beach within reach of the city. Its reputation has for several years suffered from the apparent presence of asbestos from nearby industrial plants.
 * Bari features two sea harbours: the Old Port and the New Port, constructed in 1850.

Basilica of Saint Nicholas
The Basilica di San Nicola (Saint Nicholas) was founded in 1087 to receive the relics of this saint, which were brought from Myra in Lycia, and now lie beneath the altar in the crypt. The church is one of the four Palatine churches of Apulia (the others being the cathedrals of Acquaviva delle Fonti and Altamura, and the church of Monte Sant'Angelo sul Gargano).

Bari Cathedral
Bari Cathedral, dedicated to Saint Sabinus of Canosa (San Sabino), was begun in Byzantine style in 1034, but was destroyed in the sack of the city of 1156. A new building was thus built between 1170 and 1178, partially inspired by that of San Nicola. Of the original edifice, only traces of the pavement are today visible in the transept.

Petruzzelli Theatre
The Petruzzelli Theatre, founded in 1903, hosted different forms of live entertainment, or nineteenth century "Politeama". The theatre was all but destroyed in a fire on October 27, 1991. It was reopened in October 2009, after 18 years.

Swabian Castle
The Norman-Hohenstaufen Castle, widely known as the Castello Svevo (Swabian Castle), was built by Roger II of Sicily around 1131. Destroyed in 1156, it was rebuilt by Frederick II of Hohenstaufen. The castle now serves as a gallery for a variety of temporary exhibitions in the city.

Pinacoteca Provinciale di Bari
The Pinacoteca Provinciale di Bari (Provincial Picture Gallery of Bari) is the most important art gallery in Apulia. It was first established in 1928 and contains many paintings from the 15th century up to the days of contemporary art.

The Russian Church
The Russian Church of Saint Nicholas, in the Carrassi district of Bari, was built in the early 20th century to welcome Russian pilgrims who came to the city to visit the church of Saint Nicholas in the old city where the relics of the saint remain.

The city council and Italian national government were recently involved in a trade-off with the Putin government in Moscow, exchanging the piece of land on which the church stands, for, albeit indirectly, a military barracks near Bari's central railway station.

Barivecchia
Barivecchia, or Old Bari, is a sprawl of streets and passageways making up the section of the city to the north of the modern Murat area. A large-scale redevelopment plan began with a new sewerage system, followed by the development of the two main squares, Piazza Mercantile and Piazza Ferrarese.

Demographics
, there were 316,491 people residing in Bari (about 1.6 million lived in the greater Bari area in 2015), located in the province of Bari, Apulia, of whom 47.9% were male and 52.1% were female. , minors (children ages 18 and younger) totaled 17.90 percent of the population compared to pensioners who number 19.08 percent. This compares with the Italian average of 18.06 percent (minors) and 19.94 percent (pensioners). The average age of Bari residents is 42 compared to the Italian average of 42. In the five years between 2002 and 2007, the population of Bari grew by 2.69 percent, while Italy as a whole grew by 3.56 percent. The current birth rate of Bari is 8.67 births per 1,000 inhabitants compared to the Italian average of 9.45 births.

, 3.8% of the population was foreign residents.

Migration
According to an urban migration study in Bari, return migration gain to urban areas is higher than migration loss from urban areas. People migrating from urban destinations tend to migrate to different places in comparison to people migrating from rural areas. These findings are based on the background and behavior of a sample of 211 return migrants to Bari, Italy. Bari is a port city, making it historically important because of its strong trade links with Greece, North Africa, and the eastern Mediterranean. Bari's economic structure is based on industry, commerce, services, and administration. Around two-thirds of the city's employment is in the tertiary sector with its port, commerce, and administrative functions. The highest percentage of Bari's working population is employed in services, with 45.6%. From 1958 to 1982, around 20% of migrants left Bari for other Italian communes, while around 17% or migrants came to Bari from other Italian communes. Under 2% of migrants left Bari to go abroad and came to the city from abroad.

Fiera del Levante
The Fiera del Levante, held in September in the Fiera site on the west side of Bari city center, focuses on agriculture and industry. There is also a "Fair of Nations" which displays handcrafted and locally produced goods from all over the world.

Cuisine and gastronomy

Bari's cuisine is based on three typical agricultural products found within the surrounding region of Apulia, namely wheat, olive oil and wine. The local cuisine is also enriched by the wide variety of fruit and vegetables produced locally. Local flour is used in homemade bread and pasta production including, most notably, the famous orecchiette ear-shaped pasta, recchietelle or strascinate, chiancarelle (orecchiette of different sizes) and cavatelli.

Homemade dough is also used for baked calzoni stuffed with onions, anchovies, capers, olives, etc.; fried panzerotti with mozzarella and/or ricotta forte; focaccia alla barese with tomatoes, olives and oregano; little savoury taralli, and larger friselle; and sgagliozze, fried slices of polenta; all making up the Barese culinary repertoire.

Vegetable minestrone, chick peas, broad beans, chicory, celery and fennel are also often served as first courses or side dishes.

Meat dishes and the local Barese ragù often include lamb and pork.

Pasta al forno, a baked pasta dish, is very popular in Bari and was historically a Sunday dish, or a dish used at the start of Lent when all the rich ingredients such as eggs and pork had to be used for religious reasons. The recipe commonly consists of penne or similar tubular pasta shapes, a tomato sauce, small beef and pork meatballs and halved hard-boiled eggs. The pasta is then topped with mozzarella or similar cheese and then baked in the oven to make the dish have its trademark crispy texture.

Another popular pasta dish is the spaghetti all'assassina. It is a slightly crunchy spaghetti dish, cooked in an iron pan with garlic, olive oil, chili pepper, tomato sauce and tomato broth.

Fresh fish and seafood are often eaten raw. Octopus, sea urchins and mussels feature heavily. Perhaps Bari's most famous dish is the oven-baked patate, riso e cozze (potatoes with rice and mussels).

Bari and the whole Apulian region have a range of wines, including Primitivo, Castel del Monte, and Muscat, notably Moscato di Trani.

Language
The dialect of Bari belongs to the upper-southern Italo-Romance family, and currently coexists with Italian; generally these are used in different contexts.

Sport
Local football club S.S.C. Bari, currently competing in Serie B (as of the 2022–2023 season), plays in the Stadio San Nicola, an architecturally innovative 58,000-seater stadium purpose-built for the 1990 FIFA World Cup. The stadium also hosted the 1991 European Cup final.

In 2007, Bari hosted the first and only world games for underwater sports.

Education

 * Conservatory of Bari
 * Polytechnic University of Bari
 * University of Bari

Transport
Bari has its own airport, Bari Karol Wojtyła Airport, which is located 8 km northwest of the centre of Bari. It is connected to the centre by train services from Bari Aeroporto railway station.

Bari Central Station lies on the Adriatic railway and has connection to cities such as Rome, Milan, Bologna, Turin and Venice. Another mainline is connection southwards by the Bari-Taranto railway. The Bari metropolitan railway service operates local commuter services; while regional services also operate to Foggia, Barletta, Brindisi, Lecce, Taranto and other towns and villages in the Apulia region.

Bari has an old fishery port (Porto Vecchio) and a so-called new port in the north, as well as some marinas. The Port of Bari is an important cargo transport hub to Southeast Europe. Various passenger transport lines include some seasonal ferry lines to Albania, Montenegro or Dubrovnik. Bari – Igoumenitsa is a popular ferry route to Greece. Some cruise ships call at Bari.

In popular culture
The Guido Guerrieri novels by Gianrico Carofiglio are set in Bari, where Guerrieri is a criminal lawyer, and include many descriptions of the town.

Bari is one of the primary settings of the detective novel The Black Mountain by Rex Stout. It is the characters' point of embarkation to Communist Yugoslavia.

In the 1995 film The Bridges of Madison County, Italian housewife Francesca Johnson (Meryl Streep), is mentioned as being from Bari and growing up in Naples.

The 2020 Edoardo Ponti film La vita davanti a sé, starring Sophia Loren, is set in Bari.

Notable people

 * Licia Albanese
 * Giovanni Alemanno
 * Emanuele Arciuli
 * Argyrus (catepan of Italy)
 * Francesco Attolico
 * Lino Banfi
 * Alessio Bax
 * Pope Benedict XIII
 * Gioia Bruno
 * Gianrico Carofiglio
 * Antonio Cassano
 * Riccardo Cucciolla
 * Niccolò dell'Arca
 * Chiara Fumai
 * Franco Giordano
 * Alfredo Giovine
 * Ivan Iusco
 * Gaetano Latilla
 * Guido Marzulli
 * Antonio Matarrese
 * Marco Misciagna
 * Domenico Modugno
 * Aldo Moro
 * Pomponio Nenna
 * Mario Nuzzolese
 * Joe Orlando
 * Anna Oxa
 * Pino Pascali
 * Nico Perrone
 * Niccolò Piccinni
 * Victor Posa
 * Lazarus Racanelli
 * Francesco Racanelli
 * Francesco Riefolo
 * Rocco Rodio
 * Sergio Rubini
 * Gaetano Salvemini
 * Bona Sforza
 * Cesare Stea
 * Catia Summaria
 * Pope Urban VI
 * Nichi Vendola
 * Checco Zalone
 * Dulcita Lieggi

Twin towns — sister cities
Bari is twinned with:

 * Banja Luka, Bosnia and Herzegovina
 * Batumi, Georgia
 * Corfu, Greece
 * Durrës, Albania
 * Guangzhou, China
 * Kostroma, Russia
 * Mar del Plata, Argentina
 * Monte Sant'Angelo, Italy
 * Palma de Mallorca, Spain
 * Patras, Greece
 * San Giovanni Rotondo, Italy
 * Słupsk, Poland
 * Szczecin, Poland
 * Sumgait, Azerbaijan

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Dream

A dream is a succession of images, ideas, emotions, and sensations that usually occur involuntarily in the mind during certain stages of sleep. Humans spend about two hours dreaming per night, and each dream lasts around 5 to 20 minutes, although the dreamer may perceive the dream as being much longer than this.

The content and function of dreams have been topics of scientific, philosophical and religious interest throughout recorded history. Dream interpretation, practiced by the Babylonians in the third millennium BCE and even earlier by the ancient Sumerians, figures prominently in religious texts in several traditions, and has played a lead role in psychotherapy. The scientific study of dreams is called oneirology. Most modern dream study focuses on the neurophysiology of dreams and on proposing and testing hypotheses regarding dream function. It is not known where in the brain dreams originate, if there is a single origin for dreams or if multiple regions of the brain are involved, or what the purpose of dreaming is for the body or mind.

The human dream experience and what to make of it has undergone sizable shifts over the course of history. Long ago, according to writings from Mesopotamia and Ancient Egypt, dreams dictated post-dream behaviors to an extent that was sharply reduced in later millennia. These ancient writings about dreams highlight visitation dreams, where a dream figure, usually a deity or a prominent forebear, commands the dreamer to take specific actions, and which may predict future events. Framing the dream experience varies across cultures as well as through time.

Dreaming and sleep are intertwined. Dreams occur mainly in the rapid-eye movement (REM) stage of sleep—when brain activity is high and resembles that of being awake. Because REM sleep is detectable in many species, and because research suggests that all mammals experience REM, linking dreams to REM sleep has led to conjectures that animals dream. However, humans dream during non-REM sleep, also, and not all REM awakenings elicit dream reports. To be studied, a dream must first be reduced to a verbal report, which is an account of the subject's memory of the dream, not the subject's dream experience itself. So, dreaming by non-humans is currently unprovable, as is dreaming by human fetuses and pre-verbal infants.

Subjective experience and content

Preserved writings from early Mediterranean civilizations indicate a relatively abrupt change in subjective dream experience between Bronze Age antiquity and the beginnings of the classical era.

In visitation dreams reported in ancient writings, dreamers were largely passive in their dreams, and visual content served primarily to frame authoritative auditory messaging. Gudea, the king of the Sumerian city-state of Lagash (reigned c. 2144–2124 BCE), rebuilt the temple of Ningirsu as the result of a dream in which he was told to do so. After antiquity, the passive hearing of visitation dreams largely gave way to visualized narratives in which the dreamer becomes a character who actively participates.

From the 1940s to 1985, Calvin S. Hall collected more than 50,000 dream reports at Western Reserve University. In 1966, Hall and Robert Van de Castle published The Content Analysis of Dreams, in which they outlined a coding system to study 1,000 dream reports from college students. Results indicated that participants from varying parts of the world demonstrated similarity in their dream content. The only residue of antiquity's authoritative dream figure in the Hall and Van de Castle listing of dream characters is the inclusion of God in the category of prominent persons. Hall's complete dream reports were made publicly available in the mid-1990s by his protégé William Domhoff. More recent studies of dream reports, while providing more detail, continue to cite the Hall study favorably.

In the Hall study, the most common emotion experienced in dreams was anxiety. Other emotions included abandonment, anger, fear, joy, and happiness. Negative emotions were much more common than positive ones. The Hall data analysis showed that sexual dreams occur no more than 10% of the time and are more prevalent in young to mid-teens. Another study showed that 8% of both men's and women's dreams have sexual content. In some cases, sexual dreams may result in orgasms or nocturnal emissions. These are colloquially known as "wet dreams".

The visual nature of dreams is generally highly phantasmagoric; that is, different locations and objects continuously blend into each other. The visuals (including locations, people, and objects) are generally reflective of a person's memories and experiences, but conversation can take on highly exaggerated and bizarre forms. Some dreams may even tell elaborate stories wherein the dreamer enters entirely new, complex worlds and awakes with ideas, thoughts and feelings never experienced prior to the dream.

People who are blind from birth do not have visual dreams. Their dream contents are related to other senses, such as hearing, touch, smell, and taste, whichever are present since birth.

Neurophysiology
Dream study is popular with scientists exploring the mind–brain problem. Some "propose to reduce aspects of dream phenomenology to neurobiology." But current science cannot specify dream physiology in detail. Protocols in most nations restrict human brain research to non-invasive procedures. In the United States, invasive brain procedures with a human subject are allowed only when these are deemed necessary in surgical treatment to address medical needs of the same human subject. Non-invasive measures of brain activity like electroencephalogram (EEG) voltage averaging or cerebral blood flow cannot identify small but influential neuronal populations. Also, fMRI signals are too slow to explain how brains compute in real time.

Scientists researching some brain functions can work around current restrictions by examining animal subjects. As stated by the Society for Neuroscience, "Because no adequate alternatives exist, much of this research must [sic] be done on animal subjects." However, since animal dreaming can be only inferred, not confirmed, animal studies yield no hard facts to illuminate the neurophysiology of dreams. Examining human subjects with brain lesions can provide clues, but the lesion method cannot discriminate between the effects of destruction and disconnection and cannot target specific neuronal groups in heterogeneous regions like the brain stem.

Generation

Denied precision tools and obliged to depend on imaging, much dream research has succumbed to the law of the instrument. Studies detect an increase of blood flow in a specific brain region and then credit that region with a role in generating dreams. But pooling study results has led to the newer conclusion that dreaming involves large numbers of regions and pathways, which likely are different for different dream events.

Image creation in the brain involves significant neural activity downstream from eye intake, and it is theorized that "the visual imagery of dreams is produced by activation during sleep of the same structures that generate complex visual imagery in waking perception."

Dreams present a running narrative rather than exclusively visual imagery. Following their work with split-brain subjects, Gazzaniga and LeDoux postulated, without attempting to specify the neural mechanisms, a "left-brain interpreter" that seeks to create a plausible narrative from whatever electro-chemical signals reach the brain's left hemisphere. Sleep research has determined that some brain regions fully active during waking are, during REM sleep, activated only in a partial or fragmentary way. Drawing on this knowledge, textbook author James W. Kalat explains, "[A] dream represents the brain's effort to make sense of sparse and distorted information.... The cortex combines this haphazard input with whatever other activity was already occurring and does its best to synthesize a story that makes sense of the information." Neuroscientist Indre Viskontas is even more blunt, calling often bizarre dream content "just the result of your interpreter trying to create a story out of random neural signaling."

Theories on function
For many humans across multiple eras and cultures, dreams are believed to have functioned as revealers of truths sourced during sleep from gods or other external entities. Ancient Egyptians believed that dreams were the best way to receive divine revelation, and thus they would induce (or "incubate") dreams. They went to sanctuaries and slept on special "dream beds" in hope of receiving advice, comfort, or healing from the gods. From a Darwinian perspective dreams would have to fulfill some kind of biological requirement, provide some benefit for natural selection to take place, or at least have no negative impact on fitness. Robert (1886), a physician from Hamburg, was the first who suggested that dreams are a need and that they have the function to erase (a) sensory impressions that were not fully worked up, and (b) ideas that were not fully developed during the day. In dreams, incomplete material is either removed (suppressed) or deepened and included into memory. Freud, whose dream studies focused on interpreting dreams, not explaining how or why humans dream, disputed Robert's hypothesis and proposed that dreams preserve sleep by representing as fulfilled those wishes that otherwise would awaken the dreamer. Freud wrote that dreams "serve the purpose of prolonging sleep instead of waking up. Dreams are the GUARDIANS of sleep and not its disturbers."

A turning point in theorizing about dream function came in 1953, when Science published the Aserinsky and Kleitman paper establishing REM sleep as a distinct phase of sleep and linking dreams to REM sleep. Until and even after publication of the Solms 2000 paper that certified the separability of REM sleep and dream phenomena, many studies purporting to uncover the function of dreams have in fact been studying not dreams but measurable REM sleep.

Theories of dream function since the identification of REM sleep include:

Hobson's and McCarley's 1977 activation-synthesis hypothesis, which proposed "a functional role for dreaming sleep in promoting some aspect of the learning process...." In 2010 a Harvard study was published showing experimental evidence that dreams were correlated with improved learning.

Crick's and Mitchison's 1983 "reverse learning" theory, which states that dreams are like the cleaning-up operations of computers when they are offline, removing (suppressing) parasitic nodes and other "junk" from the mind during sleep.

Hartmann's 1995 proposal that dreams serve a "quasi-therapeutic" function, enabling the dreamer to process trauma in a safe place.

Revonsuo's 2000 threat simulation hypothesis, whose premise is that during much of human evolution, physical and interpersonal threats were serious, giving reproductive advantage to those who survived them. Dreaming aided survival by replicating these threats and providing the dreamer with practice in dealing with them. In 2015, Revonsuo proposed social simulation theory, which describes dreams as a simulation for training social skills  and  bonds.

Eagleman's and Vaughn's 2021 defensive activation theory, which says that, given the brain's neuroplasticity, dreams evolved as a visual hallucinatory activity during sleep's extended periods of darkness, busying the occipital lobe and thereby protecting it from possible appropriation by other, non-vision, sense operations.

Erik Hoel proposes, based on artificial neural networks, that dreams prevent overfitting to past experiences; that is, they enable the dreamer to learn from novel situations.

Religious and other cultural contexts
Dreams figure prominently in major world religions. The dream experience for early humans, according to one interpretation, gave rise to the notion of a human "soul," a central element in much religious thought. J. W. Dunne wrote: "But there can be no reasonable doubt that the idea of a soul must have first arisen in the mind of primitive man as a result of observation of his dreams. Ignorant as he was, he could have come to no other conclusion but that, in dreams, he left his sleeping body in one universe and went wandering off into another. It is considered that, but for that savage, the idea of such a thing as a 'soul' would never have even occurred to mankind...."

Hindu
In the Mandukya Upanishad, part of the Veda scriptures of Indian Hinduism, a dream is one of three states that the soul experiences during its lifetime, the other two states being the waking state and the sleep state. The earliest Upanishads, written before 300 BCE, emphasize two meanings of dreams. The first says that dreams are merely expressions of inner desires. The second is the belief of the soul leaving the body and being guided until awakened.

Abrahamic

In Judaism, dreams are considered part of the experience of the world that can be interpreted and from which lessons can be garnered. It is discussed in the Talmud, Tractate Berachot 55–60.

The ancient Hebrews connected their dreams heavily with their religion, though the Hebrews were monotheistic and believed that dreams were the voice of one God alone. Hebrews also differentiated between good dreams (from God) and bad dreams (from evil spirits). The Hebrews, like many other ancient cultures, incubated dreams in order to receive a divine revelation. For example, the Hebrew prophet Samuel would "lie down and sleep in the temple at Shiloh before the Ark and receive the word of the Lord", and Joseph interpreted a Pharaoh's dream of seven lean cows swallowing seven fat cows as meaning the subsequent seven years would be bountiful, followed by seven years of famine. Most of the dreams in the Bible are in the Book of Genesis.

Christians mostly shared the beliefs of the Hebrews and thought that dreams were of a supernatural character because the Old Testament includes frequent stories of dreams with divine inspiration. The most famous of these dream stories was Jacob's dream of a ladder that stretches from Earth to Heaven. Many Christians preach that God can speak to people through their dreams. The famous glossary, the Somniale Danielis, written in the name of Daniel, attempted to teach Christian populations to interpret their dreams.

Iain R. Edgar has researched the role of dreams in Islam. He has argued that dreams play an important role in the history of Islam and the lives of Muslims, since dream interpretation is the only way that Muslims can receive revelations from God since the death of the last prophet, Muhammad. According to Edgar, Islam classifies three types of dreams. Firstly, there is the true dream (al-ru’ya), then the false dream, which may come from the devil (shaytan), and finally, the meaningless everyday dream (hulm). This last dream could be brought forth by the dreamer's ego or base appetite based on what they experienced in the real world. The true dream is often indicated by Islam's hadith tradition. In one narration by Aisha, the wife of the Prophet, it is said that the Prophet's dreams would come true like the ocean's waves. Just as in its predecessors, the Quran also recounts the story of Joseph and his unique ability to interpret dreams.

In both Christianity and Islam dreams feature in conversion stories. Constantine the Great started his conversion to Christianity because while on campaign he had a dream which prophecised that he would win a battle if he adopted the Chi-Rho as his battle standard.

Buddhist
In Buddhism, ideas about dreams are similar to the classical and folk traditions in South Asia. The same dream is sometimes experienced by multiple people, as in the case of the Buddha-to-be, before he is leaving his home. It is described in the Mahāvastu that several of the Buddha's relatives had premonitory dreams preceding this. Some dreams are also seen to transcend time: the Buddha-to-be has certain dreams that are the same as those of previous Buddhas, the Lalitavistara states. In Buddhist literature, dreams often function as a "signpost" motif to mark certain stages in the life of the main character.

Buddhist views about dreams are expressed in the Pāli Commentaries and the Milinda Pañhā.

Other

In Chinese history, people wrote of two vital aspects of the soul of which one is freed from the body during slumber to journey in a dream realm, while the other remained in the body. This belief and dream interpretation had been questioned since early times, such as by the philosopher Wang Chong.

The Babylonians and Assyrians divided dreams into "good," which were sent by the gods, and "bad," sent by demons. A surviving collection of dream omens entitled Iškar Zaqīqu records various dream scenarios as well as prognostications of what will happen to the person who experiences each dream, apparently based on previous cases. Some list different possible outcomes, based on occasions in which people experienced similar dreams with different results. The Greeks shared their beliefs with the Egyptians on how to interpret good and bad dreams, and the idea of incubating dreams. Morpheus, the Greek god of dreams, also sent warnings and prophecies to those who slept at shrines and temples. The earliest Greek beliefs about dreams were that their gods physically visited the dreamers, where they entered through a keyhole, exiting the same way after the divine message was given.

Antiphon wrote the first known Greek book on dreams in the 5th century BCE. In that century, other cultures influenced Greeks to develop the belief that souls left the sleeping body. The father of modern medicine, Hippocrates, thought dreams could analyze illness and predict diseases. For instance, a dream of a dim star high in the night sky indicated problems in the head region, while low in the night sky indicated bowel issues. Greek philosopher Plato (427-347) wrote that people harbor secret, repressed desires, such as incest, murder, adultery, and conquest, which build up during the day and run rampant during the night in dreams. Plato's student, Aristotle (384–322 BCE), believed dreams were caused by processing incomplete physiological activity during sleep, such as eyes trying to see while the sleeper's eyelids were closed. Marcus Tullius Cicero, for his part, believed that all dreams are produced by thoughts and conversations a dreamer had during the preceding days. Cicero's Somnium Scipionis described a lengthy dream vision, which in turn was commented on by Macrobius in his Commentarii in Somnium Scipionis.

Herodotus in his The Histories, writes "The visions that occur to us in dreams are, more often than not, the things we have been concerned about during the day."

The Dreaming is a common term within the animist creation narrative of indigenous Australians for a personal, or group, creation and for what may be understood as the "timeless time" of formative creation and perpetual creating.

Some Indigenous American tribes and Mexican populations believe that dreams are a way of visiting and having contact with their ancestors. Some Native American tribes have used vision quests as a rite of passage, fasting and praying until an anticipated guiding dream was received, to be shared with the rest of the tribe upon their return.

Interpretation

Beginning in the late 19th century, Austrian neurologist Sigmund Freud, founder of psychoanalysis, theorized that dreams reflect the dreamer's unconscious mind and specifically that dream content is shaped by unconscious wish fulfillment. He argued that important unconscious desires often relate to early childhood memories and experiences. Carl Jung and others expanded on Freud's idea that dream content reflects the dreamer's unconscious desires.

Dream interpretation can be a result of subjective ideas and experiences. One study found that most people believe that "their dreams reveal meaningful hidden truths". The researchers surveyed students in the United States, South Korea, and India, and found that 74% of Indians, 65% of South Koreans and 56% of Americans believed their dream content provided them with meaningful insight into their unconscious beliefs and desires. This Freudian view of dreaming was believed significantly more than theories of dreaming that attribute dream content to memory consolidation, problem-solving, or as a byproduct of unrelated brain activity. The same study found that people attribute more importance to dream content than to similar thought content that occurs while they are awake. Americans were more likely to report that they would intentionally miss their flight if they dreamt of their plane crashing than if they thought of their plane crashing the night before flying (while awake), and that they would be as likely to miss their flight if they dreamt of their plane crashing the night before their flight as if there was an actual plane crash on the route they intended to take. Participants in the study were more likely to perceive dreams to be meaningful when the content of dreams was in accordance with their beliefs and desires while awake. They were more likely to view a positive dream about a friend to be meaningful than a positive dream about someone they disliked, for example, and were more likely to view a negative dream about a person they disliked as meaningful than a negative dream about a person they liked.

According to surveys, it is common for people to feel their dreams are predicting subsequent life events. Psychologists have explained these experiences in terms of memory biases, namely a selective memory for accurate predictions and distorted memory so that dreams are retrospectively fitted onto life experiences. The multi-faceted nature of dreams makes it easy to find connections between dream content and real events. The term "veridical dream" has been used to indicate dreams that reveal or contain truths not yet known to the dreamer, whether future events or secrets.

In one experiment, subjects were asked to write down their dreams in a diary. This prevented the selective memory effect, and the dreams no longer seemed accurate about the future. Another experiment gave subjects a fake diary of a student with apparently precognitive dreams. This diary described events from the person's life, as well as some predictive dreams and some non-predictive dreams. When subjects were asked to recall the dreams they had read, they remembered more of the successful predictions than unsuccessful ones.

Images and literature
Graphic artists, writers and filmmakers all have found dreams to offer a rich vein for creative expression. In the West, artists' depictions of dreams in Renaissance and Baroque art often were related to Biblical narrative. Especially preferred by visual artists were the Jacob's Ladder dream in Genesis and St. Joseph's dreams in the Gospel according to Matthew.

Many later graphic artists have depicted dreams, including Japanese woodblock artist Hokusai (1760–1849) and Western European painters Rousseau (1844–1910), Picasso (1881–1973), and Dali (1904–1989).

In literature, dream frames were frequently used in medieval allegory to justify the narrative; The Book of the Duchess and The Vision Concerning Piers Plowman are two such dream visions. Even before them, in antiquity, the same device had been used by Cicero and Lucian of Samosata.

Dreams have also featured in fantasy and speculative fiction since the 19th century. One of the best-known dream worlds is Wonderland from Lewis Carroll's Alice's Adventures in Wonderland, as well as Looking-Glass Land from its sequel, Through the Looking-Glass. Unlike many dream worlds, Carroll's logic is like that of actual dreams, with transitions and flexible causality.

Other fictional dream worlds include the Dreamlands of H. P. Lovecraft's Dream Cycle and The Neverending Story's world of Fantastica, which includes places like the Desert of Lost Dreams, the Sea of Possibilities and the Swamps of Sadness. Dreamworlds, shared hallucinations and other alternate realities feature in a number of works by Philip K. Dick, such as The Three Stigmata of Palmer Eldritch and Ubik. Similar themes were explored by Jorge Luis Borges, for instance in The Circular Ruins.

Modern popular culture often conceives of dreams, as did Freud, as expressions of the dreamer's deepest fears and desires. In speculative fiction, the line between dreams and reality may be blurred even more in service to the story. Dreams may be psychically invaded or manipulated (Dreamscape, 1984; the Nightmare on Elm Street films, 1984–2010; Inception, 2010) or even come literally true (as in The Lathe of Heaven, 1971).

Lucidity
Lucid dreaming is the conscious perception of one's state while dreaming. In this state the dreamer may often have some degree of control over their own actions within the dream or even the characters and the environment of the dream. Dream control has been reported to improve with practiced deliberate lucid dreaming, but the ability to control aspects of the dream is not necessary for a dream to qualify as "lucid"—a lucid dream is any dream during which the dreamer knows they are dreaming. The occurrence of lucid dreaming has been scientifically verified.

"Oneironaut" is a term sometimes used for those who lucidly dream.

In 1975, psychologist Keith Hearne successfully recorded a communication from a dreamer experiencing a lucid dream. On April 12, 1975, after agreeing to move his eyes left and right upon becoming lucid, the subject and Hearne's co-author on the resulting article, Alan Worsley, successfully carried out this task. Years later, psychophysiologist Stephen LaBerge conducted similar work including: Communication between two dreamers has also been documented. The processes involved included EEG monitoring, ocular signaling, incorporation of reality in the form of red light stimuli and a coordinating website. The website tracked when both dreamers were dreaming and sent the stimulus to one of the dreamers where it was incorporated into the dream. This dreamer, upon becoming lucid, signaled with eye movements; this was detected by the website whereupon the stimulus was sent to the second dreamer, invoking incorporation into that dreamer's dream.
 * Using eye signals to map the subjective sense of time in dreams.
 * Comparing the electrical activity of the brain while singing awake and while dreaming.
 * Studies comparing in-dream sex, arousal, and orgasm.

Recollection

The recollection of dreams is extremely unreliable, though it is a skill that can be trained. Dreams can usually be recalled if a person is awakened while dreaming. Women tend to have more frequent dream recall than men. Dreams that are difficult to recall may be characterized by relatively little affect, and factors such as salience, arousal, and interference play a role in dream recall. Often, a dream may be recalled upon viewing or hearing a random trigger or stimulus. The salience hypothesis proposes that dream content that is salient, that is, novel, intense, or unusual, is more easily remembered. There is considerable evidence that vivid, intense, or unusual dream content is more frequently recalled. A dream journal can be used to assist dream recall, for personal interest or psychotherapy purposes.

Adults report remembering around two dreams per week, on average. Unless a dream is particularly vivid and if one wakes during or immediately after it, the content of the dream is typically not remembered.

In line with the salience hypothesis, there is considerable evidence that people who have more vivid, intense or unusual dreams show better recall. There is evidence that continuity of consciousness is related to recall. Specifically, people who have vivid and unusual experiences during the day tend to have more memorable dream content and hence better dream recall. People who score high on measures of personality traits associated with creativity, imagination, and fantasy, such as openness to experience, daydreaming, fantasy proneness, absorption, and hypnotic susceptibility, tend to show more frequent dream recall. There is also evidence for continuity between the bizarre aspects of dreaming and waking experience. That is, people who report more bizarre experiences during the day, such as people high in schizotypy (psychosis proneness), have more frequent dream recall and also report more frequent nightmares.

Dream-recording machine
Recording or reconstructing dreams may one day assist with dream recall. Using the permitted non-invasive technologies, functional magnetic resonance imaging (fMRI) and electromyography (EMG), researchers have been able to identify basic dream imagery, dream speech activity and dream motor behavior (such as walking and hand movements).

Illusion of reality
Some philosophers have proposed that what we think of as the "real world" could be or is an illusion (an idea known as the skeptical hypothesis about ontology). The first recorded mention of the idea was in the 4th century BCE by Zhuangzi, and in Eastern philosophy, the problem has been named the "Zhuangzi Paradox." "He who dreams of drinking wine may weep when morning comes; he who dreams of weeping may in the morning go off to hunt. While he is dreaming he does not know it is a dream, and in his dream he may even try to interpret a dream. Only after he wakes does he know it was a dream. And someday there will be a great awakening when we know that this is all a great dream. Yet the stupid believe they are awake, busily and brightly assuming they understand things, calling this man ruler, that one herdsman—how dense! Confucius and you are both dreaming! And when I say you are dreaming, I am dreaming, too. Words like these will be labeled the Supreme Swindle. Yet, after ten thousand generations, a great sage may appear who will know their meaning, and it will still be as though he appeared with astonishing speed."

The idea also is discussed in Hindu and Buddhist writings. It was formally introduced to Western philosophy by Descartes in the 17th century in his Meditations on First Philosophy.

Absent-minded transgression
Dreams of absent-minded transgression (DAMT) are dreams wherein the dreamer absent-mindedly performs an action that he or she has been trying to stop (one classic example is of a quitting smoker having dreams of lighting a cigarette). Subjects who have had DAMT have reported waking with intense feelings of guilt. One study found a positive association between having these dreams and successfully stopping the behavior.

Non-REM dreams
Hypnogogic and hypnopompic dreams, dreamlike states shortly after falling asleep and shortly before awakening, and dreams during stage 2 of NREM-sleep, also occur, but are shorter than REM-dreams.

Daydreams

A daydream is a visionary fantasy, especially one of happy, pleasant thoughts, hopes or ambitions, imagined as coming to pass, and experienced while awake. There are many different types of daydreams, and there is no consistent definition amongst psychologists. The general public also uses the term for a broad variety of experiences. Research by Harvard psychologist Deirdre Barrett has found that people who experience vivid dreamlike mental images reserve the word for these, whereas many other people refer to milder imagery, realistic future planning, review of memories or just "spacing out"—i.e. one's mind going relatively blank—when they talk about "daydreaming".

While daydreaming has long been derided as a lazy, non-productive pastime, it is now commonly acknowledged that daydreaming can be constructive in some contexts. There are numerous examples of people in creative or artistic careers, such as composers, novelists and filmmakers, developing new ideas through daydreaming. Similarly, research scientists, mathematicians and physicists have developed new ideas by daydreaming about their subject areas.

Hallucination
A hallucination, in the broadest sense of the word, is a perception in the absence of a stimulus. In a stricter sense, hallucinations are perceptions in a conscious and awake state, in the absence of external stimuli, and have qualities of real perception, in that they are vivid, substantial, and located in external objective space. The latter definition distinguishes hallucinations from the related phenomena of dreaming, which does not involve wakefulness.

Nightmare

A nightmare is an unpleasant dream that can cause a strong negative emotional response from the mind, typically fear or horror, but also despair, anxiety and great sadness. The dream may contain situations of danger, discomfort, psychological or physical terror. Sufferers usually awaken in a state of distress and may be unable to return to sleep for a prolonged period of time.

Night terror
A night terror, also known as a sleep terror or pavor nocturnus, is a parasomnia disorder that predominantly affects children, causing feelings of terror or dread. Night terrors should not be confused with nightmares, which are bad dreams that cause the feeling of horror or fear.

Déjà vu
One theory of déjà vu attributes the feeling of having previously seen or experienced something to having dreamed about a similar situation or place, and forgetting about it until one seems to be mysteriously reminded of the situation or the place while awake.

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

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Up to

Two mathematical objects $a$ and $b$ are called "equal up to an equivalence relation $R$"
 * if $a$ and $b$ are related by $R$, that is,
 * if $aRb$ holds, that is,
 * if the equivalence classes of $a$ and $b$ with respect to $R$ are equal.

This figure of speech is mostly used in connection with expressions derived from equality, such as uniqueness or count. For example, "$x$ is unique up to $R$" means that all objects $x$ under consideration are in the same equivalence class with respect to the relation $R$.

Moreover, the equivalence relation $R$ is often designated rather implicitly by a generating condition or transformation. For example, the statement "an integer's prime factorization is unique up to ordering" is a concise way to say that any two lists of prime factors of a given integer are equivalent with respect to the relation $R$ that relates two lists if one can be obtained by reordering (permuting) the other. As another example, the statement "the solution to an indefinite integral is $sin(x)$, up to addition of a constant" tacitly employs the equivalence relation $R$ between functions, defined by $fRg$ if the difference $f−g$ is a constant function, and means that the solution and the function $sin(x)$ are equal up to this $R$. In the picture, "there are 4 partitions up to rotation" means that the set $P$ has 4 equivalence classes with respect to $R$ defined by $aRb$ if $b$ can be obtained from $a$ by rotation; one representative from each class is shown in the bottom left picture part.

Equivalence relations are often used to disregard possible differences of objects, so "up to $R$" can be understood informally as "ignoring the same subtleties as $R$ ignores". In the factorization example, "up to ordering" means "ignoring the particular ordering".

Further examples include "up to isomorphism", "up to permutations", and "up to rotations", which are described in the Examples section.

In informal contexts, mathematicians often use the word modulo (or simply mod) for similar purposes, as in "modulo isomorphism".

Tetris
Consider the seven Tetris pieces (I, J, L, O, S, T, Z), known mathematically as the tetrominoes. If you consider all the possible rotations of these pieces — for example, if you consider the "I" oriented vertically to be distinct from the "I" oriented horizontally — then you find there are 19 distinct possible shapes to be displayed on the screen. (These 19 are the so-called "fixed" tetrominoes. ) But if rotations are not considered distinct — so that we treat both "I vertically" and "I horizontally" indifferently as "I" — then there are only seven. We say that "there are seven tetrominoes, up to rotation". One could also say that "there are five tetrominoes, up to rotation and reflection", which accounts for the fact that L reflected gives J, and S reflected gives Z.

Eight queens
In the eight queens puzzle, if the queens are considered to be distinct (e.g. if they are colored with eight different colors), then there are 3709440 distinct solutions. Normally, however, the queens are considered to be interchangeable, and one usually says "there are $3,709,440 / 8! = 92$ unique solutions up to permutation of the queens", or that "there are 92 solutions modulo the names of the queens", signifying that two different arrangements of the queens are considered equivalent if the queens have been permuted, as long as the set of occupied squares remains the same.

If, in addition to treating the queens as identical, rotations and reflections of the board were allowed, we would have only 12 distinct solutions "up to symmetry and the naming of the queens". For more, see.

Polygons
The regular $n$-gon, for a fixed $n$, is unique up to similarity. In other words, the "similarity" equivalence relation over the regular $n$-gons (for a fixed $n$) has only one equivalence class; it is impossible to produce two regular $n$-gons which are not similar to each other.

Group theory
In group theory, one may have a group $G$ acting on a set $X$, in which case, one might say that two elements of $X$ are equivalent "up to the group action"—if they lie in the same orbit.

Another typical example is the statement that "there are two different groups of order 4 up to isomorphism", or "modulo isomorphism, there are two groups of order 4". This means that, if one considers isomorphic groups "equivalent", there are only two equivalence classes of groups of order 4.

Nonstandard analysis
A hyperreal $x$ and its standard part $st(x)$ are equal up to an infinitesimal difference.

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Barcellona Pozzo di Gotto

Barcellona Pozzo di Gotto (Sicilian: Baccialona Pizzaottu) is a town and comune of about 50,000 inhabitants in the north coast of Sicily, Italy, 40 km from Messina towards Palermo. It belongs to the Metropolitan City of Messina.

Ancient history
In the area corresponding to the current municipal area, the following ancient settlements were identified:

 * Settlement and necropolis of the Bronze Age and Iron Age, in Maloto locality.
 * Settlement and necropolis, from around the 10th century BC, in Pizzo Lando.
 * Settlement and necropolis of ancient Greek or Hellenistic times, assigned to 8th century BC, in Oliveto locality.
 * Settlement and necropolis of Sicani/Greek origins, dating from around the 6th and 5th centuries BC, in Sant'Onofrio locality.

In 265 BC, the Battle of Longano, between the army of Hiero II of Syracuse and the Mamertines under the command of the leader Cione, took place in this area. The exact assignment of the place in the absence of identifiable cause remains earthquakes, floods, or diversion of water courses. There are several hypotheses that place the event along the courses of the rivers bordering the "Mela" or "Patrì", and other in the vicinity of the mythical city "Longane" (Rodì Milici) or "Abacena" (Tripi), however settlements related to the same conflict.

Origins and etymology

Barcellona Pozzo di Gotto lies in the plain that slopes to the north close to the lush hills and the chain of Peloritani mountains, overlooking the Gulf of Patti in the Tyrrhenian Sea on the part near the Aeolian Islands in a portion of coast between the Milazzo peninsula to the east and to the west promontory of Tindari.

The most creditable hypothesis for the roots to its name lies in the domination of the Crown of Aragon (1282–1516) and then in the five hundred year history of Spanish Sicily (1516–1713), flowing together with the Kingdom of Naples under the jurisdiction of the Crown of Spain. The same analogy have identified the first conquerors from County of Aragon and County of Barcelona.

The oldest part of the town, Pozzo di Gotto, owes its name to the digging of a well for irrigation in cultivated lands located between the rivers Idria and Longano, belonging to Nicholas Goto as described in Vulgar Latin in a document dated 1463: " ... Nicolao de Gotho, ..., in quo Puzzo de Gotho ...". In 1571 Pozzogottesi obtained from the Grand Court of the Archbishop of Messina permission to elect their chaplain stationed in Saint Vitus no longer depend from Archpriest of Milazzo. Gained recognition, has advanced the redemption request to the Court of Madrid against the oppressive power of Milazzo under whose jurisdiction Pozzo di Gotto depended politically and physically by providing a distant hamlet, a bond that will be permanently discontinued 22 May 1639, and ratified by royal decree Viceroy under the reign of Philip IV of Spain, assumes the title "Libera et Realis Civitas Putei de Gotho". The village in the west of the river Longano in turn under the jurisdiction of Castroreale and had already followed the example of the neighboring community, rebelling against the jurors castrensian doing in the Church to recognize its independence. Notarial deeds dating back to 1522 in Castroreale report the name of the district or hamlet of "Barsalona", a name likely to be attributed to the presence in the baptismal books of Pozzo di Gotto the name of "Graziosa Barsalona", on the other hand is supported the thesis that the name of the location has been given by Iberian sailors having recognizing the remarkable similarity of the two territories.

The autonomy of the village of Barcellona was accepted by the Sicilian Parliament, recognized by the King on 15 May 1815 and ratified in Wien 28 February 1823, by King Ferdinand I of the Two Sicilies. The administrative union decreed 5 January 1835, comes into force on 1 June 1836 at the behest of King Ferdinand II of the Two Sicilies, deciding that the new municipality formed by the merger of the two ancient districts bore the full name of Barcellona Pozzo di Gotto. Are discarded by the King all the advanced options of names derived from the word "Longano", receiving the unanimous appreciation, on the other hand the initial goodwill will turn into hatred and resentment towards the monarch as a result of criminal actions undertaken throughout the province, especially in Milazzo and Messina, which earned him the nickname of "King Bomb". The city soon established covered a certain role with significant contributions to the definitive expulsion of the House of Bourbon from the province and the whole of Sicily and increasingly effective input in all the events included in the process of unification of constituting Kingdom of Italy.

Traditions and folklore
The procession of Varette which takes place on Friday, when for parade through the streets of the city at the same time two processions consist of twenty-six Vare depicting the mysteries of the Passion, Easter Rites included in the "Santa Sumana".

Main sights
The thirteenth-century village of Castroreale, home to a tower from a medieval castle built by King Frederick II of Aragon, is located nearby.

The Nello Cassata Ethnohistory Museum is based here.

People

 * Giuseppa Bolognara Calcagno (1846–1884), freedom fighter of the Risorgimento
 * Emilio Fede (1931–), journalist
 * Carmelo Freni (1934-) journalist, writer, director
 * Emilio Isgrò (1937–), artist
 * Leonardo Vitale (1941–1984), Mafia pentito
 * Francesca Chillemi (1985–), Miss Italia 2003

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Luminosity

Luminosity is an absolute measure of radiated electromagnetic energy (light) per unit time, and is synonymous with the radiant power emitted by a light-emitting object. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a star, galaxy, or other astronomical objects.

In SI units, luminosity is measured in joules per second, or watts. In astronomy, values for luminosity are often given in the terms of the luminosity of the Sun, L⊙. Luminosity can also be given in terms of the astronomical magnitude system: the absolute bolometric magnitude (Mbol) of an object is a logarithmic measure of its total energy emission rate, while absolute magnitude is a logarithmic measure of the luminosity within some specific wavelength range or filter band.

In contrast, the term brightness in astronomy is generally used to refer to an object's apparent brightness: that is, how bright an object appears to an observer. Apparent brightness depends on both the luminosity of the object and the distance between the object and observer, and also on any absorption of light along the path from object to observer. Apparent magnitude is a logarithmic measure of apparent brightness. The distance determined by luminosity measures can be somewhat ambiguous, and is thus sometimes called the luminosity distance.

Measurement
When not qualified, the term "luminosity" means bolometric luminosity, which is measured either in the SI units, watts, or in terms of solar luminosities. A bolometer is the instrument used to measure radiant energy over a wide band by absorption and measurement of heating. A star also radiates neutrinos, which carry off some energy (about 2% in the case of the Sun), contributing to the star's total luminosity. The IAU has defined a nominal solar luminosity of $3.83 watts$ to promote publication of consistent and comparable values in units of the solar luminosity.

While bolometers do exist, they cannot be used to measure even the apparent brightness of a star because they are insufficiently sensitive across the electromagnetic spectrum and because most wavelengths do not reach the surface of the Earth. In practice bolometric magnitudes are measured by taking measurements at certain wavelengths and constructing a model of the total spectrum that is most likely to match those measurements. In some cases, the process of estimation is extreme, with luminosities being calculated when less than 1% of the energy output is observed, for example with a hot Wolf-Rayet star observed only in the infrared. Bolometric luminosities can also be calculated using a bolometric correction to a luminosity in a particular passband.

The term luminosity is also used in relation to particular passbands such as a visual luminosity of K-band luminosity. These are not generally luminosities in the strict sense of an absolute measure of radiated power, but absolute magnitudes defined for a given filter in a photometric system. Several different photometric systems exist. Some such as the UBV or Johnson system are defined against photometric standard stars, while others such as the AB system are defined in terms of a spectral flux density.

Stellar luminosity
A star's luminosity can be determined from two stellar characteristics: size and effective temperature. The former is typically represented in terms of solar radii, R⊙, while the latter is represented in kelvins, but in most cases neither can be measured directly. To determine a star's radius, two other metrics are needed: the star's angular diameter and its distance from Earth. Both can be measured with great accuracy in certain cases, with cool supergiants often having large angular diameters, and some cool evolved stars having masers in their atmospheres that can be used to measure the parallax using VLBI. However, for most stars the angular diameter or parallax, or both, are far below our ability to measure with any certainty. Since the effective temperature is merely a number that represents the temperature of a black body that would reproduce the luminosity, it obviously cannot be measured directly, but it can be estimated from the spectrum.

An alternative way to measure stellar luminosity is to measure the star's apparent brightness and distance. A third component needed to derive the luminosity is the degree of interstellar extinction that is present, a condition that usually arises because of gas and dust present in the interstellar medium (ISM), the Earth's atmosphere, and circumstellar matter. Consequently, one of astronomy's central challenges in determining a star's luminosity is to derive accurate measurements for each of these components, without which an accurate luminosity figure remains elusive. Extinction can only be measured directly if the actual and observed luminosities are both known, but it can be estimated from the observed colour of a star, using models of the expected level of reddening from the interstellar medium.

In the current system of stellar classification, stars are grouped according to temperature, with the massive, very young and energetic Class O stars boasting temperatures in excess of 30,000 K while the less massive, typically older Class M stars exhibit temperatures less than 3,500 K. Because luminosity is proportional to temperature to the fourth power, the large variation in stellar temperatures produces an even vaster variation in stellar luminosity. Because the luminosity depends on a high power of the stellar mass, high mass luminous stars have much shorter lifetimes. The most luminous stars are always young stars, no more than a few million years for the most extreme. In the Hertzsprung–Russell diagram, the x-axis represents temperature or spectral type while the y-axis represents luminosity or magnitude. The vast majority of stars are found along the main sequence with blue Class O stars found at the top left of the chart while red Class M stars fall to the bottom right. Certain stars like Deneb and Betelgeuse are found above and to the right of the main sequence, more luminous or cooler than their equivalents on the main sequence. Increased luminosity at the same temperature, or alternatively cooler temperature at the same luminosity, indicates that these stars are larger than those on the main sequence and they are called giants or supergiants.

Blue and white supergiants are high luminosity stars somewhat cooler than the most luminous main sequence stars. A star like Deneb, for example, has a luminosity around 200,000 L⊙, a spectral type of A2, and an effective temperature around 8,500 K, meaning it has a radius around 203 solar radius. For comparison, the red supergiant Betelgeuse has a luminosity around 100,000 L⊙, a spectral type of M2, and a temperature around 3,500 K, meaning its radius is about 1000 solar radius. Red supergiants are the largest type of star, but the most luminous are much smaller and hotter, with temperatures up to 50,000 K and more and luminosities of several million L⊙, meaning their radii are just a few tens of R⊙. For example, R136a1 has a temperature over 46,000 K and a luminosity of more than 6,100,000 L⊙ (mostly in the UV), it is only 39 solar radius.

Radio luminosity
The luminosity of a radio source is measured in $W Hz^{−1}$, to avoid having to specify a bandwidth over which it is measured. The observed strength, or flux density, of a radio source is measured in Jansky where $1 Jy = 10^{−26} W m^{−2} Hz^{−1}$.

For example, consider a 10W transmitter at a distance of 1 million metres, radiating over a bandwidth of 1 MHz. By the time that power has reached the observer, the power is spread over the surface of a sphere with area $4πr^{2}$ or about $1.26×10^{13} m^{2}$, so its flux density is $10 / 10^{6} / (1.26×10^{13}) W m^{−2} Hz^{−1} = 8×10^{7} Jy$.

More generally, for sources at cosmological distances, a k-correction must be made for the spectral index α of the source, and a relativistic correction must be made for the fact that the frequency scale in the emitted rest frame is different from that in the observer's rest frame. So the full expression for radio luminosity, assuming isotropic emission, is $$L_{\nu} = \frac{S_{\mathrm{obs}} 4 \pi {D_{L}}^{2}}{(1+z)^{1+\alpha}}$$ where Lν is the luminosity in $W Hz^{−1}$, Sobs is the observed flux density in $W m^{−2} Hz^{−1}$, DL is the luminosity distance in metres, z is the redshift, α is the spectral index (in the sense $$I \propto {\nu}^{\alpha}$$, and in radio astronomy, assuming thermal emission the spectral index is typically equal to 2.)

For example, consider a 1 Jy signal from a radio source at a redshift of 1, at a frequency of 1.4 GHz. Ned Wright's cosmology calculator calculates a luminosity distance for a redshift of 1 to be 6701 Mpc = 2×1026 m giving a radio luminosity of $10^{−26} × 4\pi(2×10^{26})^{2} / (1 + 1)^{(1 + 2)} = 6×10^{26} W Hz^{−1}$.

To calculate the total radio power, this luminosity must be integrated over the bandwidth of the emission. A common assumption is to set the bandwidth to the observing frequency, which effectively assumes the power radiated has uniform intensity from zero frequency up to the observing frequency. In the case above, the total power is $4×10^{27} × 1.4×10^{9} = 5.7×10^{36} W$. This is sometimes expressed in terms of the total (i.e. integrated over all wavelengths) luminosity of the Sun which is $3.86×10^{26} W$, giving a radio power of $1.5×10^{10} L_{⊙}$.

Luminosity formulae

The Stefan–Boltzmann equation applied to a black body gives the value for luminosity for a black body, an idealized object which is perfectly opaque and non-reflecting: $$L = \sigma A T^4,$$ where A is the surface area, T is the temperature (in kelvins) and $σ$ is the Stefan–Boltzmann constant, with a value of

Imagine a point source of light of luminosity $$L$$ that radiates equally in all directions. A hollow sphere centered on the point would have its entire interior surface illuminated. As the radius increases, the surface area will also increase, and the constant luminosity has more surface area to illuminate, leading to a decrease in observed brightness.

$$F = \frac{L}{A},$$ where
 * $$A$$ is the area of the illuminated surface.
 * $$F$$ is the flux density of the illuminated surface.

The surface area of a sphere with radius r is $$A = 4\pi r^2$$, so for stars and other point sources of light: $$F = \frac{L}{4\pi r^2} \,,$$ where $$r$$ is the distance from the observer to the light source.

For stars on the main sequence, luminosity is also related to mass approximately as below: $$\frac{L}{L_{\odot}} \approx {\left ( \frac{M}{M_{\odot}} \right )}^{3.5}.$$

Relationship to magnitude
Luminosity is an intrinsic measurable property of a star independent of distance. The concept of magnitude, on the other hand, incorporates distance. The apparent magnitude is a measure of the diminishing flux of light as a result of distance according to the inverse-square law. The Pogson logarithmic scale is used to measure both apparent and absolute magnitudes, the latter corresponding to the brightness of a star or other celestial body as seen if it would be located at an interstellar distance of 10 parsec. In addition to this brightness decrease from increased distance, there is an extra decrease of brightness due to extinction from intervening interstellar dust.

By measuring the width of certain absorption lines in the stellar spectrum, it is often possible to assign a certain luminosity class to a star without knowing its distance. Thus a fair measure of its absolute magnitude can be determined without knowing its distance nor the interstellar extinction.

In measuring star brightnesses, absolute magnitude, apparent magnitude, and distance are interrelated parameters—if two are known, the third can be determined. Since the Sun's luminosity is the standard, comparing these parameters with the Sun's apparent magnitude and distance is the easiest way to remember how to convert between them, although officially, zero point values are defined by the IAU.

The magnitude of a star, a unitless measure, is a logarithmic scale of observed visible brightness. The apparent magnitude is the observed visible brightness from Earth which depends on the distance of the object. The absolute magnitude is the apparent magnitude at a distance of 10 parsec, therefore the bolometric absolute magnitude is a logarithmic measure of the bolometric luminosity.

The difference in bolometric magnitude between two objects is related to their luminosity ratio according to: $$M_\text{bol1} - M_\text{bol2} = -2.5 \log_{10}\frac{L_\text{1}}{L_\text{2}}$$

where:
 * $$M_{\text{bol1}}$$ is the bolometric magnitude of the first object
 * $$M_\text{bol2}$$ is the bolometric magnitude of the second object.
 * $$L_\text{1}$$ is the first object's bolometric luminosity
 * $$L_\text{2}$$ is the second object's bolometric luminosity

The zero point of the absolute magnitude scale is actually defined as a fixed luminosity of $4 L_{⊙}$. Therefore, the absolute magnitude can be calculated from a luminosity in watts: $$M_\mathrm{bol} = -2.5 \log_{10} \frac{L_{*}}{L_0} \approx -2.5 \log_{10} L_{*} + 71.1974$$ where $L_{0}$ is the zero point luminosity $3.828 W$

and the luminosity in watts can be calculated from an absolute magnitude (although absolute magnitudes are often not measured relative to an absolute flux): $$L_{*} = L_0 \times 10^{-0.4 M_\mathrm{bol}}$$

title: Luminosity


text:
Battle of Dunbar

Battle of Dunbar may refer to:
 * Battle of Dunbar (1296), a battle in the Wars of Scottish Independence
 * Battle of Dunbar (1650), a battle in the 1650 to 1652 Anglo-Scottish War

title: Battle of Dunbar


text:
User:Zisa

Started in Wikipedia around 2001. Has been doing some technical stuff and book related stuff as profession(s). Locations as a Wikipedian have varied; now Austin. Texas, before that Cork, Palermo... Has lived e.g. in Brazil, Italy, UK, Finland, Spain, USA, Ireland and some other countries. Was born in the mid-late 1970s on Earth, and according to the state registries that was in two quite distant places. Happily taken. Languages: Italian, Spanish, English, Portuguese, Sicilian, and a list of others.

Addictions or characters, among which topics are also the user contributions to Wikipedia: Apple Computer, Macintosh, World Wide Web, Sicily, South America, Argentina, Brazil, Colombia, graphics, software, Palermo, mafia, ndrangheta, organized criminal systems (against), middleages, 1182 (year), Buenos Aires, Octavio Paz, hacking, Buddhism, Carlos Castaneda, 1349, W, Astor Piazzolla, modern tango, Kevin Mitnick, Steve Jobs, Linux RedHat, freebsd, Darwin, Mac OS X (with all its flavors since 10.0), VMware etc etc.

title: User:Zisa


text:
Emergency Medical Treatment and Active Labor Act

The Emergency Medical Treatment and Active Labor Act (EMTALA) is an act of the United States Congress, passed in 1986 as part of the Consolidated Omnibus Budget Reconciliation Act (COBRA). It requires hospital emergency departments that accept payments from Medicare to provide an appropriate medical screening examination (MSE) for anyone seeking treatment for a medical condition regardless of citizenship, legal status, or ability to pay. Participating hospitals may not transfer or discharge patients needing emergency treatment except with the informed consent or stabilization of the patient or when the patient's condition requires transfer to a hospital better equipped to administer the treatment.

EMTALA applies to "participating hospitals." The statute defines participating hospitals as those that accept payment from the Department of Health and Human Services', Centers for Medicare and Medicaid Services (CMS) under the Medicare program. Because there are very few hospitals that do not accept Medicare, the law applies to nearly all hospitals. The combined payments of Medicare and Medicaid, $602 billion in 2004, or roughly 44% of all medical expenditures in the United States, make not participating in EMTALA impractical for nearly all hospitals. EMTALA's provisions apply to all patients, not just to Medicare patients.

The cost of emergency care required by EMTALA is not covered directly by the federal government, so it has been characterized as an unfunded mandate. In 2009, uncompensated care represents 55% of emergency room care, and 6% of total hospital costs.

Prior legislation
The Hill-Burton Act of 1946, which provided federal assistance for the construction of community hospitals, established nondiscrimination requirements for institutions that received such federal assistance—including the requirement that a "reasonable volume" of free emergency care be provided for community members who could not pay—for a period for 20 years after the hospital's construction. Amendments to the act in 1975 removed the 20-year expiration date and instead required hospitals receiving Hill-Burton funding to provide free care in perpetuity. However, the provisions of the act were vague and rarely enforced.

Mandated and non-mandated care
Congress passed EMTALA to eliminate the practice of "patient dumping"—that is, refusal to treat people because of inability to pay or insufficient insurance or transferring or discharging emergency patients on the basis of high anticipated diagnosis and treatment costs. The law applies when an individual seeks treatment for a medical condition "or a request is made on the individual's behalf for examination or treatment for that medical condition."

The U.S. government defines an emergency department as "a specially equipped and staffed area of the hospital used a significant portion of the time for initial evaluation and treatment of outpatients for emergency medical conditions." That means, for example, that outpatient clinics not equipped to handle medical emergencies are not obligated under EMTALA and can simply refer patients to a nearby emergency department for care.

An emergency medical condition (EMC) is defined as "a condition manifesting itself by acute symptoms of sufficient severity (including severe pain) such that the absence of immediate medical attention could reasonably be expected to result in placing the individual's health [or the health of an unborn child] in serious jeopardy, serious impairment to bodily functions, or serious dysfunction of bodily organs." For example, a pregnant woman with an emergency condition and/or currently in labor must be treated until delivery is complete, until the woman and the fetus are stabilized, or until a qualified personnel identifies the labor as a "false labor" or Braxton Hicks contractions, unless a transfer under the statute is appropriate.

Patients treated under EMTALA may not be able to pay or have insurance or other programs pay for the associated costs but are legally responsible for any costs incurred as a result of their care under civil law.

Non-covered medical conditions
Not all medical conditions qualify for uncompensated mandated services imposed by EMTALA, which is contrary to the misperception that many individuals assume: that if they are ill, they will be treated regardless of their ability to pay.

The sole purpose of the EMTALA-mandated MSE is to require emergency departments to make a determination about whether an emergency medical condition does or does not exist, using their normal assessment and diagnostic protocols. Because the MSE is a mandated EMTALA service, health insurers are required to cover benefits for their subscribers. They are also required to cover EMTALA mandated services necessary to stabilize individuals determined to have an EMC.

EMTALA intentionally omitted requirements that hospitals provide uncompensated stabilizing treatment for individuals with medical conditions determined not to be EMCs. Therefore, such individuals are not eligible for further uncompensated examination and treatment beyond the MSE.

A significant portion of emergency department visits are considered not to be EMCs as defined by EMTALA. The medical profession refers to such cases as "non-emergent". Regardless, the term is not recognized by law as a condition defined by the EMTALA statute. A term more relevant for compliance with EMTALA is "non-emergency medical condition". If the "non-emergent" term is used in the context of EMTALA, it must be defined as a medical condition that fails to pass the criteria for determination of being a true EMC as defined by EMTALA statute.

Admitted patients who experience a medical emergency while at a hospital are normally not covered by EMTALA but are instead protected by varying state laws and quality assurance under the deemed status of the facility.

Hospital obligations
Hospitals have three obligations under EMTALA:
 * 1) An individual requesting emergency care or one for whom a representative has made a request if the patient is unable to do so must receive a medical screening examination (MSE) to determine whether an emergency medical condition (EMC) exists. The participating hospital cannot delay examination and treatment to inquire about methods of payment, insurance coverage, or a patient's citizenship or legal status. The hospital may start the process of payment inquiry and billing only once it has ensured that doing so will not interfere with or otherwise compromise patient care.
 * 2) When an emergency department determines that an individual has an EMC, the hospital must provide further treatment and examination until the EMC is resolved or stabilized and the patient can provide self-care after discharge or, if unable to do so, can receive needed continual care. Inpatient care provided must be at an equal level for all patients regardless of ability to pay. Hospitals cannot discharge a patient prior to stabilization if the patient's insurance is canceled or if the patient otherwise discontinues payment during the course of stay.
 * 3) If the hospital does not have the capability to treat the condition, the hospital must make an "appropriate" transfer of the patient to another hospital with such capability. That includes long-term-care or rehabilitation facilities for patients unable to provide self-care. Hospitals with specialized capabilities must accept such transfers and may not discharge a patient until the condition is resolved and the patient is able to provide self-care or is transferred to another facility. A hospital has no obligation under EMTALA to provide uncompensated services beyond the screening exam unless it determines that the patient has an EMC.

Amendments
Since the act's original passage, the Congress has passed several amendments to the act. Additionally, state and local laws in some places have imposed further requirements on hospitals. The amendments include the following:
 * A patient is defined as "stable", therefore ending a hospital's EMTALA obligations, if:
 * The patient is conscious, alert, and oriented.
 * The cause of all symptoms reported by the patient or representative and all potentially life-threatening, limb-threatening, or organ-threatening symptoms discovered by hospital staff have been ascertained to the best of the hospital's ability.
 * Any conditions that are immediately life-threatening, limb-threatening, or organ-threatening have been treated to the best of the hospital's ability to ensure the patient does not need further, inpatient care.
 * The patient is able to care for himself or herself with or without special equipment, which, if needed, must be provided. The required abilities are:
 * Breathing
 * Feeding
 * Mobility
 * Dressing
 * Personal hygiene
 * Toileting
 * Medicating
 * Communication
 * Another competent person is available and able to meet the patient's needs after discharge.
 * All patients have EMTALA rights equally regardless of age, race, religion, nationality, ethnicity, residence, citizenship, or legal status. If a patient's status is found to be illegal, hospitals may not discharge the patient prior to completion of care, but law enforcement and hospital security may take necessary actions to prevent a patient from escaping or harming others. Treatment may be delayed as needed only to prevent patients from harming themselves or others.
 * Overloaded hospitals may not discharge a patient unable to pay so they can make room for a patient who is able to pay or is otherwise viewed by society as a more-valued citizen. If the emergency department is overloaded, patients must be treated in an order based on their determined medical needs, not their ability to pay.
 * Hospitals may not deny or provide substandard services for a patient who already has outstanding debt to the hospital and may not withhold the patient's belongings, records, or other required services until the patient pays.
 * Hospitals and related services cannot receive a judgment against the patient in court filings made more than 36 months after the date the patient was discharged or the last partial payment the patient made to the hospital, contractor, or agent. After that period, the patient may not be threatened with legal action if payment is not made and may not be denied future outpatient services from the same company or agency that a patient is able to pay.
 * If a patient has been awarded monetary damages against a hospital or any related or affiliated services by a court of law or has settled out of court on damages, the hospital and related or affiliated services may neither withhold money for lack of payment nor count the money toward the bill in lieu of making payment to the patient. Voluntary consent for such an arrangement is permitted only if initiated by the patient. A hospital may not threaten or coerce a patient into such a settlement or mislead the patient into believing such an arrangement is required or recommended.
 * Patients cannot face criminal prosecution for failure to pay even if the patients become aware of inability to pay the hospital. Hospitals and third-party agents may not threaten patients with prosecution as a means of scaring patients into making payment. Patients can be prosecuted under existing federal, state, or local laws for providing false names, addresses, or other information to avoid payment, to avoid receiving bills, or to hide fugitive status.
 * A hospital cannot delay treatment while determining whether a patient can pay or is insured, but that does not mean the hospital is completely forbidden from asking for or running a credit check. If a patient fails to pay the bill, the hospital can sue the patient, and the unsatisfied judgment will likely appear on the patient's credit report. A third-party collector for a hospital bill would be covered under the Fair Debt Collection Practices Act.
 * Hospitals are prohibited from discriminating against or providing substandard care for patients who appear impoverished or homeless, are not well-dressed or well-groomed, or exhibit signs of mental illness or intoxication. If the hospital fears that a patient may be a threat to others, the hospital may delay care only as necessary to protect others.
 * Hospitals are required to sufficiently feed patients unable to pay at a level equal to those able to pay and must meet all physician-ordered dietary restrictions.
 * Hospitals are not required to provide premium services for a patient that are not related to medical care (such as television) when failure to provide that service does not compromise patient care.
 * Hospitals and affiliated clinics may avoid providing continued outpatient care, drugs, or other supplies after discharge. If such services are recommended but a patient is unable to pay, the hospital is required to refer the patient to a clinic or tax-funded or private program that enables the patient to pay for such services and to which the patient has reasonable access. Hospitals must reasonably assist a patient as necessary to obtain such services by providing information as the patient requests.

Improved health services for uninsured patients
The most significant effect is that regardless of insurance status, participating hospitals are prohibited from denying an MSE of individuals seeking treatment for medical conditions. Currently, EMTALA requires only that hospitals stabilize the EMC. According to some analyses of the U.S. health care social safety net, EMTALA is an incomplete and strained program.

Cost pressures on hospitals
According to the Centers for Medicare & Medicaid Services, 55% of U.S. emergency care now goes uncompensated. When medical bills go unpaid, health care providers must either shift the costs onto those who can pay or go uncompensated. In the first decade of EMTALA, such cost shifting amounted to a hidden tax levied by providers. For example, it has been estimated that cost shifting has amounted to $455 per individual, or $1,186 per family, in California annually.

However, because of the recent influence of managed care and other cost control initiatives by insurance companies, hospitals are less able to shift costs, and they end up writing off more and more in uncompensated care. The amount of uncompensated care delivered by nonfederal community hospitals grew from $6.1 billion in 1983 to $40.7 billion in 2004, according to a 2004 report from the Kaiser Commission on Medicaid and the Uninsured, but it is unclear what percentage of the amount was emergency care and therefore attributable to EMTALA.

Financial pressures on hospitals in the 20 years since EMTALA's passage have caused hospitals to consolidate or close facilities, thereby contributing to emergency department overcrowding. According to the Institute of Medicine, from 1993 to 2003, emergency department visits in the United States grew by 26 percent, while in the same period, the number of emergency departments declined by 425. Ambulances frequently get diverted from overcrowded emergency departments to other hospitals that may be farther away. In 2003, ambulances got diverted more than half a million times—not necessarily due to patients' inability to pay.

Emergency abortions
After Roe v. Wade (1973) was overturned in June 2022, transforming the legal landscape for abortion in the United States, the HHS issued guidance on EMTALA protections for clinicians that apply regardless of state laws. According to the guidance, which does not change policy, EMTALA, as a federal law, supersedes state laws that ban abortion. So, doctors who perform emergency abortions to stabilize a patient are protected by EMTALA. Hospitals that fail to do so could face fines or be booted from Medicare. The guidance also says EMTALA does not prevent a doctor from being sued, though EMTALA may be used in defense of the doctor in state court actions.

The Biden administration filed a motion in federal court to block Idaho's enforcement of that state's abortion ban in cases in which EMTALA applied. The judge ruled against the state and ordered Idaho's law suspended in emergency cases. Idaho appealed the ruling, arguing that the federal government “cannot use EMTALA to override in the emergency room state laws about abortion any more than it can use it to override state law on organ transplants or marijuana use.” The Supreme Court agreed to hear Idaho's challenge to that interpretation of the law in Moyle v. United States (2024), which was argued that April.

Texas sued the federal government, winning in federal court. A 5th Circuit judge preliminarily enjoined the Biden administration's EMTALA guidance in Texas.

In June 2024, the Supreme Court issued a 63 ruling in Moyle which reinstated the lower court ruling requiring EMTALA's emergency abortion provision to be enforced in Idaho. However, the issue remains unresolved, with the ruling only seen as delaying the Idaho state law banning emergency abortions rather than striking it down altogether. However, the Supreme Court ruling did allow for the case to return to a lower court which was previously favorable to upholding EMTALA's emergency abortion provision.