Urban heat island
An urban heat island is an urban area or metropolitan area, warmer than its surrounding rural areas due to human activities. The temperature difference is larger at night than during the day, is most apparent when winds are weak. UHI is most noticeable during the winter; the main cause of the urban heat island effect is from the modification of land surfaces. Waste heat generated by energy usage is a secondary contributor; as a population center grows, it tends to increase its average temperature. The term heat island is used. Monthly rainfall is greater downwind of cities due to the UHI. Increases in heat within urban centers increases the length of growing seasons, decreases the occurrence of weak tornadoes; the UHI decreases air quality by increasing the production of pollutants such as ozone, decreases water quality as warmer waters flow into area streams and put stress on their ecosystems. Not all cities have a distinct urban heat island. Mitigation of the urban heat island effect can be accomplished through the use of green roofs and the use of lighter-colored surfaces in urban areas, which reflect more sunlight and absorb less heat.
Concerns have been raised about possible contribution from urban heat islands to global warming. While some lines of research did not detect a significant impact, other studies have concluded that heat islands can have measurable effects on climate phenomena at the global scale; the phenomenon was first investigated and described by Luke Howard in the 1810s, although he was not the one to name the phenomenon. There are several causes of an urban heat island; this causes a change in the energy budget of the urban area leading to higher temperatures than surrounding rural areas. Another major reason is the lack of evapotranspiration in urban areas; the U. S. Forest Service found in 2018 that cities in the United States are losing 36 million trees each year. With a decreased amount of vegetation, cities lose the shade and evaporative cooling effect of trees. Other causes of a UHI are due to geometric effects; the tall buildings within many urban areas provide multiple surfaces for the reflection and absorption of sunlight, increasing the efficiency with which urban areas are heated.
This is called the "urban canyon effect". Another effect of buildings is the blocking of wind, which inhibits cooling by convection and prevents pollutants from dissipating. Waste heat from automobiles, air conditioning and other sources contributes to the UHI. High levels of pollution in urban areas can increase the UHI, as many forms of pollution change the radiative properties of the atmosphere. UHI not only raises urban temperatures but increases ozone concentrations because ozone is a green house gas whose formation will accelerate with the increase of temperature; some cities exhibit largest at night. Seasonally, UHI shows up both in winter; the typical temperature difference is several degrees between the center of the city and surrounding fields. The difference in temperature between an inner city and its surrounding suburbs is mentioned in weather reports, as in "68 °F downtown, 64 °F in the suburbs". "The annual mean air temperature of a city with 1 million people or more can be 1.8–5.4 °F warmer than its surroundings.
In the evening, the difference can be as high as 22 °F."The UHI can be defined as either the air temperature difference or the surface temperature difference between the urban and the rural area. These two show different diurnal and seasonal variability and have different causes The IPCC stated that "it is well-known that compared to non-urban areas urban heat islands raise night-time temperatures more than daytime temperatures." For example, Spain is 0.2 °C cooler for daily maxima and 2.9 °C warmer for minima than a nearby rural station. A description of the first report of the UHI by Luke Howard in the late 1810s said that the urban center of London was warmer at night than the surrounding countryside by 3.7 °F. Though the warmer air temperature within the UHI is most apparent at night, urban heat islands exhibit significant and somewhat paradoxical diurnal behavior; the air temperature difference between the UHI and the surrounding environment is large at night and small during the day. The opposite is true for skin temperatures of the urban landscape within the UHI.
Throughout the daytime when the skies are cloudless, urban surfaces are warmed by the absorption of solar radiation. Surfaces in the urban areas tend to warm faster than those of the surrounding rural areas. By virtue of their high heat capacities, urban surfaces act as a giant reservoir of heat energy. For example, concrete can hold 2,000 times as much heat as an equivalent volume of air; as a result, the large daytime surface temperature within the UHI is seen via thermal remote sensing. As is the case with daytime heating, this warming has the effect of generating convective winds within
A picnic is a meal taken outdoors as part of an excursion – ideally in scenic surroundings, such as a park, lakeside, or other place affording an interesting view, or else in conjunction with a public event such as preceding an open-air theatre performance, in summer. Picnics are meant for the late mornings or midday breakfasts, but could be held as a luncheonette or a dinner event. Descriptions of picnics show that the idea of a meal, jointly contributed and was enjoyed out-of-doors was essential to a picnic from the early 19th century. Picnics are family oriented but can be an intimate occasion between two people or a large get together such as company picnics and church picnics, it is sometimes combined with a cookout a form of barbecue: either grilling, baking, or a combination of all of the above. On romantic and family picnics, a picnic basket and a blanket are brought along. Outdoor games or some other form of entertainment are common at large picnics. In established public parks, a picnic area includes picnic tables and other items related to eating outdoors, such as built-in grills, water faucets, garbage containers, restrooms.
Some picnics are a potluck, an entertainment at which each person contributed some dish to a common table for all to share. When the picnic is not a cookout, the food eaten is hot, instead taking the form of deli sandwiches, finger food, fresh fruit, cold meats and accompanied by chilled wine or champagne or soft drinks; the first usage of the word is traced to the 1692 edition of Tony Willis, Origines de la Langue Française, which mentions pique-nique as being of recent origin. The term was used to describe a group of people dining in a restaurant; the concept of a picnic long retained the connotation of a meal to which everyone contributed something. Whether picnic is based on the verb piquer which means'pick' or'peck' with the rhyming nique meaning "thing of little importance" is doubted. Picnicking was common in France after the French Revolution, when it became possible for ordinary people to visit and mingle in the country’s royal parks. In 18th and 19th centuries, picnics were elaborate social events with complex meals and fancy drinks that sometimes took days to prepare.
The word picnic first appeared in English in a letter of the Gallicized Lord Chesterfield in 1748, who associates it with card-playing and conversation, may have entered the English language from this French word. The practice of an elegant meal eaten out-of-doors, rather than an agricultural worker's dinner in a field, was connected with respite from hunting from the Middle Ages. Though it may have appeared in a 17th-century dictionary as "pique-nique," the actual usage began as "pique un niche" meaning to "pick a place," an isolated spot where family or friends could enjoy a jolly meal together away from the distractions and public nature of a communal life; the term after years of usage entered the official French language. Despite having been debunked, a spurious etymology linking the origin of the word to lynchings of African-Americans in the American South continues to resurface from time to time. After the French Revolution in 1789, royal parks became open to the public for the first time.
Picnicking in the parks became a popular activity amongst the newly enfranchised citizens. Early in the 19th century, a fashionable group of Londoners formed the'Picnic Society'. Members met in the Pantheon on Oxford Street; each member was expected to provide a share of the entertainment and of the refreshments with no one particular host. Interest in the society waned in the 1850s. From the 1830s, Romantic American landscape painting of spectacular scenery included a group of picnickers in the foreground. An early American illustration of the picnic is Thomas Cole's The Pic-Nic of 1846. In it, a guitarist serenades the genteel social group in the Hudson River Valley with the Catskills visible in the distance. Cole's well-dressed young picnickers having finished their repast, served from splint baskets on blue-and-white china, stroll about in the woodland and boat on the lake; the image of picnics as a peaceful social activity can be utilised for political protest, too. In this context, a picnic functions as a temporary occupation of significant public territory.
A famous example of this is the Pan-European Picnic held on both sides of the Hungarian/Austrian border on the 19 August 1989 as part of the struggle towards German reunification. In 2000, a 600-mile-long picnic took place from coast to coast in France to celebrate the first Bastille Day of the new Millennium. In the United States the 4 July celebration of American independence is a popular day for a picnic. In Italy, the favorite picnic day is Easter Monday; the 1955 film Picnic, based on the Pulitzer Prize-winning play by William Inge, was a multiple Oscar winner. The film has been remade twice, in 1986 and 2000. Picnickers are used to illustrate the scale of one metre in the film Powers of Ten; the Office Picnic is a dark comedy set in an Australian Public Service office. It was written and produced by filmmaker Tom Cowan, now famous for his work on the series Survivor. In Peter Weir's myst
A skyscraper is a continuously habitable high-rise building that has over 40 floors and is taller than 150 m. The term first referred to buildings with 10 to 20 floors in the 1880s; the definition shifted with advancing construction technology during the 20th century. Skyscrapers may host both. For buildings above a height of 300 m, the term "supertall" can be used, while skyscrapers reaching beyond 600 m are classified as "megatall". One common feature of skyscrapers is having a steel framework; these curtain walls either bear on the framework below or are suspended from the framework above, rather than resting on load-bearing walls of conventional construction. Some early skyscrapers have a steel frame that enables the construction of load-bearing walls taller than of those made of reinforced concrete. Modern skyscrapers' walls are not load-bearing, most skyscrapers are characterized by large surface areas of windows made possible by steel frames and curtain walls. However, skyscrapers can have curtain walls that mimic conventional walls with a small surface area of windows.
Modern skyscrapers have a tubular structure, are designed to act like a hollow cylinder to resist wind and other lateral loads. To appear more slender, allow less wind exposure, transmit more daylight to the ground, many skyscrapers have a design with setbacks, which are sometimes structurally required; the term "skyscraper" was first applied to buildings of steel framed construction of at least 10 stories in the late 19th century, a result of public amazement at the tall buildings being built in major American cities like Chicago, New York City, Detroit, St. Louis; the first steel-frame skyscraper was the Home Insurance Building in Chicago, Illinois in 1885. Some point to Philadelphia's 10-story Jayne Building as a proto-skyscraper, or to New York's seven-floor Equitable Life Building, built in 1870, for its innovative use of a kind of skeletal frame, but such designation depends on what factors are chosen; the scholars making the argument find it to be purely academic. The structural definition of the word skyscraper was refined by architectural historians, based on engineering developments of the 1880s that had enabled construction of tall multi-story buildings.
This definition was based on the steel skeleton—as opposed to constructions of load-bearing masonry, which passed their practical limit in 1891 with Chicago's Monadnock Building. What is the chief characteristic of the tall office building? It is lofty, it must be tall. The force and power of altitude must be in it, the glory and pride of exaltation must be in it, it must be every inch a proud and soaring thing, rising in sheer exaltation that from bottom to top it is a unit without a single dissenting line. — Louis Sullivan's The Tall Office Building Artistically Considered The Council on Tall Buildings and Urban Habitat defines skyscrapers as those buildings which reach or exceed 150 m in height. Others in the United States and Europe draw the lower limit of a skyscraper at 150 m; the Emporis Standards Committee defines a high-rise building as "a multi-story structure between 35–100 meters tall, or a building of unknown height from 12–39 floors" and a skyscraper as "a multi-story building whose architectural height is at least 100 m or 330 ft."
Some structural engineers define a highrise as any vertical construction for which wind is a more significant load factor than earthquake or weight. Note that this criterion fits not only high-rises but some other tall structures, such as towers; the word skyscraper carries a connotation of pride and achievement. The skyscraper, in name and social function, is a modern expression of the age-old symbol of the world center or axis mundi: a pillar that connects earth to heaven and the four compass directions to one another; the tallest building in ancient times was the 146 m Great Pyramid of Giza in ancient Egypt, built in the 26th century BC. It was not surpassed in height for thousands of years, the 160 m Lincoln Cathedral having exceeded it in 1311–1549, before its central spire collapsed; the latter in turn was not surpassed until the 555-foot Washington Monument in 1884. However, being uninhabited, none of these structures comply with the modern definition of a skyscraper. High-rise apartments flourished in classical antiquity.
Ancient Roman insulae in imperial cities reached 10 and more stories. Beginning with Augustus, several emperors attempted to establish limits of 20–25 m for multi-story buildings, but met with only limited success. Lower floors were occupied by shops or wealthy families, the upper rented to the lower classes. Surviving Oxyrhynchus Papyri indicate that seven-story buildings existed in provincial towns such as in 3rd century AD Hermopolis in Roman Egypt; the skylines of many important medieval cities had large numbers of high-rise urban towers, built by the wealthy for defense and status. The residential Towers of 12th century Bologna numbered between 80 and 100 at a time, the tallest of, the 97.2 m high Asinelli Tower. A Florentine law of 1251 decreed that all urban buildings be reduced to less than 26 m. Medium-sized towns of the era are known to have proliferations of towers, such as the 72 up to 51 m height in San Gimignano; the medieval Egyptian city of Fustat housed many high-rise residential buildings, which Al-Muqaddasi in the 10th century described as resembling minarets.
Nasir Khusraw in the early 11th century described some of them rising up to 14 stories, with roof gardens on t
The United States of America known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U. S. is the third most populous country. The capital is Washington, D. C. and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico; the State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean; the U. S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The diverse geography and wildlife of the United States make it one of the world's 17 megadiverse countries.
Paleo-Indians migrated from Siberia to the North American mainland at least 12,000 years ago. European colonization began in the 16th century; the United States emerged from the thirteen British colonies established along the East Coast. Numerous disputes between Great Britain and the colonies following the French and Indian War led to the American Revolution, which began in 1775, the subsequent Declaration of Independence in 1776; the war ended in 1783 with the United States becoming the first country to gain independence from a European power. The current constitution was adopted in 1788, with the first ten amendments, collectively named the Bill of Rights, being ratified in 1791 to guarantee many fundamental civil liberties; the United States embarked on a vigorous expansion across North America throughout the 19th century, acquiring new territories, displacing Native American tribes, admitting new states until it spanned the continent by 1848. During the second half of the 19th century, the Civil War led to the abolition of slavery.
By the end of the century, the United States had extended into the Pacific Ocean, its economy, driven in large part by the Industrial Revolution, began to soar. The Spanish–American War and World War I confirmed the country's status as a global military power; the United States emerged from World War II as a global superpower, the first country to develop nuclear weapons, the only country to use them in warfare, a permanent member of the United Nations Security Council. Sweeping civil rights legislation, notably the Civil Rights Act of 1964, the Voting Rights Act of 1965 and the Fair Housing Act of 1968, outlawed discrimination based on race or color. During the Cold War, the United States and the Soviet Union competed in the Space Race, culminating with the 1969 U. S. Moon landing; the end of the Cold War and the collapse of the Soviet Union in 1991 left the United States as the world's sole superpower. The United States is the world's oldest surviving federation, it is a representative democracy.
The United States is a founding member of the United Nations, World Bank, International Monetary Fund, Organization of American States, other international organizations. The United States is a developed country, with the world's largest economy by nominal GDP and second-largest economy by PPP, accounting for a quarter of global GDP; the U. S. economy is post-industrial, characterized by the dominance of services and knowledge-based activities, although the manufacturing sector remains the second-largest in the world. The United States is the world's largest importer and the second largest exporter of goods, by value. Although its population is only 4.3% of the world total, the U. S. holds 31% of the total wealth in the world, the largest share of global wealth concentrated in a single country. Despite wide income and wealth disparities, the United States continues to rank high in measures of socioeconomic performance, including average wage, human development, per capita GDP, worker productivity.
The United States is the foremost military power in the world, making up a third of global military spending, is a leading political and scientific force internationally. In 1507, the German cartographer Martin Waldseemüller produced a world map on which he named the lands of the Western Hemisphere America in honor of the Italian explorer and cartographer Amerigo Vespucci; the first documentary evidence of the phrase "United States of America" is from a letter dated January 2, 1776, written by Stephen Moylan, Esq. to George Washington's aide-de-camp and Muster-Master General of the Continental Army, Lt. Col. Joseph Reed. Moylan expressed his wish to go "with full and ample powers from the United States of America to Spain" to seek assistance in the revolutionary war effort; the first known publication of the phrase "United States of America" was in an anonymous essay in The Virginia Gazette newspaper in Williamsburg, Virginia, on April 6, 1776. The second draft of the Articles of Confederation, prepared by John Dickinson and completed by June 17, 1776, at the latest, declared "The name of this Confederation shall be the'United States of America'".
The final version of the Articles sent to the states for ratification in late 1777 contains the sentence "The Stile of this Confederacy shall be'The United States of America'". In June 1776, Thomas Jefferson wrote the phrase "UNITED STATES OF AMERICA" in all capitalized letters in the headline of his "original Rough draught" of the Declaration of Independence; this draft of the document did not surface unti
Argentina the Argentine Republic, is a country located in the southern half of South America. Sharing the bulk of the Southern Cone with Chile to the west, the country is bordered by Bolivia and Paraguay to the north, Brazil to the northeast and the South Atlantic Ocean to the east, the Drake Passage to the south. With a mainland area of 2,780,400 km2, Argentina is the eighth-largest country in the world, the fourth largest in the Americas, the largest Spanish-speaking nation; the sovereign state is subdivided into twenty-three provinces and one autonomous city, Buenos Aires, the federal capital of the nation as decided by Congress. The provinces and the capital exist under a federal system. Argentina claims sovereignty over part of Antarctica, the Falkland Islands, South Georgia and the South Sandwich Islands; the earliest recorded human presence in modern-day Argentina dates back to the Paleolithic period. The Inca Empire expanded to the northwest of the country in Pre-Columbian times; the country has its roots in Spanish colonization of the region during the 16th century.
Argentina rose as the successor state of the Viceroyalty of the Río de la Plata, a Spanish overseas viceroyalty founded in 1776. The declaration and fight for independence was followed by an extended civil war that lasted until 1861, culminating in the country's reorganization as a federation of provinces with Buenos Aires as its capital city; the country thereafter enjoyed relative peace and stability, with several waves of European immigration radically reshaping its cultural and demographic outlook. The almost-unparalleled increase in prosperity led to Argentina becoming the seventh wealthiest nation in the world by the early 20th century. Following the Great Depression in the 1930s, Argentina descended into political instability and economic decline that pushed it back into underdevelopment, though it remained among the fifteen richest countries for several decades. Following the death of President Juan Perón in 1974, his widow, Isabel Martínez de Perón, ascended to the presidency, she was overthrown in 1976 by a U.
S.-backed coup which installed a right-wing military dictatorship. The military government persecuted and murdered numerous political critics and leftists in the Dirty War, a period of state terrorism that lasted until the election of Raúl Alfonsín as President in 1983. Several of the junta's leaders were convicted of their crimes and sentenced to imprisonment. Argentina is a prominent regional power in the Southern Cone and Latin America, retains its historic status as a middle power in international affairs. Argentina has the second largest economy in South America, the third-largest in Latin America, membership in the G-15 and G-20 major economies, it is a founding member of the United Nations, World Bank, World Trade Organization, Union of South American Nations, Community of Latin American and Caribbean States and the Organization of Ibero-American States. Despite its history of economic instability, it ranks second highest in the Human Development Index in Latin America; the description of the country by the word Argentina has been found on a Venetian map in 1536.
In English the name "Argentina" comes from the Spanish language, however the naming itself is not Spanish, but Italian. Argentina means in Italian " of silver, silver coloured" borrowed from the Old French adjective argentine " of silver" > "silver coloured" mentioned in the 12th century. The French word argentine is the feminine form of argentin and derives from argent "silver" with the suffix -in; the Italian naming "Argentina" for the country implies Terra Argentina "land of silver" or Costa Argentina "coast of silver". In Italian, the adjective or the proper noun is used in an autonomous way as a substantive and replaces it and it is said l'Argentina; the name Argentina was first given by the Venetian and Genoese navigators, such as Giovanni Caboto. In Spanish and Portuguese, the words for "silver" are plata and prata and " of silver" is said plateado and prateado. Argentina was first associated with the silver mountains legend, widespread among the first European explorers of the La Plata Basin.
The first written use of the name in Spanish can be traced to La Argentina, a 1602 poem by Martín del Barco Centenera describing the region. Although "Argentina" was in common usage by the 18th century, the country was formally named "Viceroyalty of the Río de la Plata" by the Spanish Empire, "United Provinces of the Río de la Plata" after independence; the 1826 constitution included the first use of the name "Argentine Republic" in legal documents. The name "Argentine Confederation" was commonly used and was formalized in the Argentine Constitution of 1853. In 1860 a presidential decree settled the country's name as "Argentine Republic", that year's constitutional amendment ruled all the names since 1810 as valid. In the English language the country was traditionally called "the Argentine", mimicking the typical Spanish usage la Argentina and resulting from a mistaken shortening of the fuller name'Argentine Republic'.'The Argentine' fell out of fashion during the mid-to-late 20th century, now the country is referred to as "Argentina".
In the Spanish language "Argentina" is feminine, taking the feminine article "La" as the i
Brazil the Federative Republic of Brazil, is the largest country in both South America and Latin America. At 8.5 million square kilometers and with over 208 million people, Brazil is the world's fifth-largest country by area and the fifth most populous. Its capital is Brasília, its most populated city is São Paulo; the federation is composed of the union of the 26 states, the Federal District, the 5,570 municipalities. It is the largest country to have Portuguese as an official language and the only one in the Americas. Bounded by the Atlantic Ocean on the east, Brazil has a coastline of 7,491 kilometers, it borders all other South American countries except Ecuador and Chile and covers 47.3% of the continent's land area. Its Amazon River basin includes a vast tropical forest, home to diverse wildlife, a variety of ecological systems, extensive natural resources spanning numerous protected habitats; this unique environmental heritage makes Brazil one of 17 megadiverse countries, is the subject of significant global interest and debate regarding deforestation and environmental protection.
Brazil was inhabited by numerous tribal nations prior to the landing in 1500 of explorer Pedro Álvares Cabral, who claimed the area for the Portuguese Empire. Brazil remained a Portuguese colony until 1808, when the capital of the empire was transferred from Lisbon to Rio de Janeiro. In 1815, the colony was elevated to the rank of kingdom upon the formation of the United Kingdom of Portugal and the Algarves. Independence was achieved in 1822 with the creation of the Empire of Brazil, a unitary state governed under a constitutional monarchy and a parliamentary system; the ratification of the first constitution in 1824 led to the formation of a bicameral legislature, now called the National Congress. The country became a presidential republic in 1889 following a military coup d'état. An authoritarian military junta came to power in 1964 and ruled until 1985, after which civilian governance resumed. Brazil's current constitution, formulated in 1988, defines it as a democratic federal republic. Due to its rich culture and history, the country ranks thirteenth in the world by number of UNESCO World Heritage Sites.
Brazil is considered an advanced emerging economy. It has the ninth largest GDP in the world by nominal, eight and PPP measures, it is one of the world's major breadbaskets, being the largest producer of coffee for the last 150 years. It is classified as an upper-middle income economy by the World Bank and a newly industrialized country, with the largest share of global wealth in Latin America. Brazil is a regional power and sometimes considered a great or a middle power in international affairs. On account of its international recognition and influence, the country is subsequently classified as an emerging power and a potential superpower by several analysts. Brazil is a founding member of the United Nations, the G20, BRICS, Union of South American Nations, Organization of American States, Organization of Ibero-American States and the Community of Portuguese Language Countries, it is that the word "Brazil" comes from the Portuguese word for brazilwood, a tree that once grew plentifully along the Brazilian coast.
In Portuguese, brazilwood is called pau-brasil, with the word brasil given the etymology "red like an ember", formed from brasa and the suffix -il. As brazilwood produces a deep red dye, it was valued by the European textile industry and was the earliest commercially exploited product from Brazil. Throughout the 16th century, massive amounts of brazilwood were harvested by indigenous peoples along the Brazilian coast, who sold the timber to European traders in return for assorted European consumer goods; the official Portuguese name of the land, in original Portuguese records, was the "Land of the Holy Cross", but European sailors and merchants called it the "Land of Brazil" because of the brazilwood trade. The popular appellation eclipsed and supplanted the official Portuguese name; some early sailors called it the "Land of Parrots". In the Guarani language, an official language of Paraguay, Brazil is called "Pindorama"; this was the name the indigenous population gave to the region, meaning "land of the palm trees".
Some of the earliest human remains found in the Americas, Luzia Woman, were found in the area of Pedro Leopoldo, Minas Gerais and provide evidence of human habitation going back at least 11,000 years. The earliest pottery found in the Western Hemisphere was excavated in the Amazon basin of Brazil and radiocarbon dated to 8,000 years ago; the pottery was found near Santarém and provides evidence that the tropical forest region supported a complex prehistoric culture. The Marajoara culture flourished on Marajó in the Amazon delta from 800 CE to 1400 CE, developing sophisticated pottery, social stratification, large populations, mound building, complex social formations such as chiefdoms. Around the time of the Portuguese arrival, the territory of current day Brazil had an estimated indigenous population of 7 million people semi-nomadic who subsisted on hunting, fishing and migrant agriculture; the indigenous population of Brazil comprised several large indigenous ethnic groups. The Tupí people were subdivided into the Tupiniquins and Tupinambás, there were many subdivisions of the other gro
A city is a large human settlement. Cities have extensive systems for housing, sanitation, land use, communication, their density facilitates interaction between people, government organizations and businesses, sometimes benefiting different parties in the process. City-dwellers have been a small proportion of humanity overall, but following two centuries of unprecedented and rapid urbanization half of the world population now lives in cities, which has had profound consequences for global sustainability. Present-day cities form the core of larger metropolitan areas and urban areas—creating numerous commuters traveling towards city centers for employment and edification. However, in a world of intensifying globalization, all cities are in different degree connected globally beyond these regions; the most populated city proper is Chongqing while the most populous metropolitan areas are the Greater Tokyo Area, the Shanghai area, Jabodetabek. The cities of Faiyum and Varanasi are among those laying claim to longest continual inhabitation.
A city is distinguished from other human settlements by its great size, but by its functions and its special symbolic status, which may be conferred by a central authority. The term can refer either to the physical streets and buildings of the city or to the collection of people who dwell there, can be used in a general sense to mean urban rather than rural territory. A variety of definitions, invoking population, population density, number of dwellings, economic function, infrastructure, are used in national censuses to classify populations as urban. Common population definitions for a city range between 1,500 and 50,000 people, with most U. S. states using a minimum between 5,000 inhabitants. However, some jurisdictions set no such minimums. In the United Kingdom, city status is awarded by the government and remains permanently, resulting in some small cities, such as Wells and St Davids. According to the "functional definition" a city is not distinguished by size alone, but by the role it plays within a larger political context.
Cities serve as administrative, commercial and cultural hubs for their larger surrounding areas. Examples of settlements called city which may not meet any of the traditional criteria to be named such include Broad Top City and City Dulas, Anglesey, a hamlet; the presence of a literate elite is sometimes included in the definition. A typical city has professional administrators and some form of taxation to support the government workers; the governments may be based on heredity, military power, work projects such as canal building, food distribution, land ownership, commerce, finance, or a combination of these. Societies that live in cities are called civilizations; the word city and the related civilization come, via Old French, from the Latin root civitas meaning citizenship or community member and coming to correspond with urbs, meaning city in a more physical sense. The Roman civitas was linked with the Greek "polis"—another common root appearing in English words such as metropolis. Urban geography deals both with their internal structure.
Town siting has varied through history according to natural, technological and military contexts. Access to water has long been a major factor in city placement and growth, despite exceptions enabled by the advent of rail transport in the nineteenth century, through the present most of the world's urban population lives near the coast or on a river. Urban areas as a rule cannot produce their own food and therefore must develop some relationship with a hinterland which sustains them. Only in special cases such as mining towns which play a vital role in long-distance trade, are cities disconnected from the countryside which feeds them. Thus, centrality within a productive region influences siting, as economic forces would in theory favor the creation of market places in optimal mutually reachable locations; the vast majority of cities have a central area containing buildings with special economic and religious significance. Archaeologists refer to this area by the Greek term temenos; these spaces reflect and amplify the city's centrality and importance to its wider sphere of influence.
Today cities have downtown, sometimes coincident with a central business district. Cities have public spaces where anyone can go; these include owned spaces open to the public as well as forms of public land such as public domain and the commons. Western philosophy since the time of the Greek agora has considered physical public space as the substrate of the symbolic public sphere. Public art adorns public spaces. Parks and other natural sites within cities provide residents with relief from the hardness and regularity of typical built environments. Urban structure follows one or more basic patterns: geomorphic, concentric and curvilinear. Physical environment constrains the form in which a city is built. If located on a mountainside, urban structure may rely on winding roads, it may be adapted to its means of subsistence. And it may be set up for optimal defense given the surrounding landscape. Beyond these "geomorphi