The United Kingdom the United Kingdom of Great Britain and Northern Ireland, sometimes referred to as Britain, is a sovereign country located off the north-western coast of the European mainland. The United Kingdom includes the island of Great Britain, the north-eastern part of the island of Ireland, many smaller islands. Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state, the Republic of Ireland. Apart from this land border, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to the east, the English Channel to the south and the Celtic Sea to the south-west, giving it the 12th-longest coastline in the world; the Irish Sea lies between Great Ireland. With an area of 242,500 square kilometres, the United Kingdom is the 78th-largest sovereign state in the world, it is the 22nd-most populous country, with an estimated 66.0 million inhabitants in 2017. The UK is constitutional monarchy; the current monarch is Queen Elizabeth II, who has reigned since 1952, making her the longest-serving current head of state.
The United Kingdom's capital and largest city is London, a global city and financial centre with an urban area population of 10.3 million. Other major urban areas in the UK include Greater Manchester, the West Midlands and West Yorkshire conurbations, Greater Glasgow and the Liverpool Built-up Area; the United Kingdom consists of four constituent countries: England, Scotland and Northern Ireland. Their capitals are London, Edinburgh and Belfast, respectively. Apart from England, the countries have their own devolved governments, each with varying powers, but such power is delegated by the Parliament of the United Kingdom, which may enact laws unilaterally altering or abolishing devolution; the nearby Isle of Man, Bailiwick of Guernsey and Bailiwick of Jersey are not part of the UK, being Crown dependencies with the British Government responsible for defence and international representation. The medieval conquest and subsequent annexation of Wales by the Kingdom of England, followed by the union between England and Scotland in 1707 to form the Kingdom of Great Britain, the union in 1801 of Great Britain with the Kingdom of Ireland created the United Kingdom of Great Britain and Ireland.
Five-sixths of Ireland seceded from the UK in 1922, leaving the present formulation of the United Kingdom of Great Britain and Northern Ireland. There are fourteen British Overseas Territories, the remnants of the British Empire which, at its height in the 1920s, encompassed a quarter of the world's land mass and was the largest empire in history. British influence can be observed in the language and political systems of many of its former colonies; the United Kingdom is a developed country and has the world's fifth-largest economy by nominal GDP and ninth-largest economy by purchasing power parity. It has a high-income economy and has a high Human Development Index rating, ranking 14th in the world, it was the world's first industrialised country and the world's foremost power during the 19th and early 20th centuries. The UK remains a great power, with considerable economic, military and political influence internationally, it is sixth in military expenditure in the world. It has been a permanent member of the United Nations Security Council since its first session in 1946.
It has been a leading member state of the European Union and its predecessor, the European Economic Community, since 1973. The United Kingdom is a member of the Commonwealth of Nations, the Council of Europe, the G7, the G20, NATO, the Organisation for Economic Co-operation and Development and the World Trade Organization; the 1707 Acts of Union declared that the kingdoms of England and Scotland were "United into One Kingdom by the Name of Great Britain". The term "United Kingdom" has been used as a description for the former kingdom of Great Britain, although its official name from 1707 to 1800 was "Great Britain"; the Acts of Union 1800 united the kingdom of Great Britain and the kingdom of Ireland in 1801, forming the United Kingdom of Great Britain and Ireland. Following the partition of Ireland and the independence of the Irish Free State in 1922, which left Northern Ireland as the only part of the island of Ireland within the United Kingdom, the name was changed to the "United Kingdom of Great Britain and Northern Ireland".
Although the United Kingdom is a sovereign country, Scotland and Northern Ireland are widely referred to as countries. The UK Prime Minister's website has used the phrase "countries within a country" to describe the United Kingdom; some statistical summaries, such as those for the twelve NUTS 1 regions of the United Kingdom refer to Scotland and Northern Ireland as "regions". Northern Ireland is referred to as a "province". With regard to Northern Ireland, the descriptive name used "can be controversial, with the choice revealing one's political preferences"; the term "Great Britain" conventionally refers to the island of Great Britain, or politically to England and Wales in combination. However, it is sometimes used as a loose synonym for the United Kingdom as a whole; the term "Britain" is used both as a synonym for Great Britain, as a synonym for the United Kingdom. Usage is mixed, with the BBC preferring to use Britain as shorthand only for Great Britain and the UK Government, while accepting that both terms refer to the United K
The Russian Wikipedia is the Russian-language edition of Wikipedia. As of April 2019, it has 1,540,644 articles, it was started on 11 May 2001. In October 2015 it became the sixth-largest Wikipedia by the number of articles, it has the fifth-largest number of edits. Since 2016, Alexa Internet rankings tend to show it as the world's most visited language Wikipedia after the English Wikipedia, it is the largest Wikipedia written in any Slavic language, surpassing its nearest rival, the Polish Wikipedia, eightfold by the parameter of depth. In addition, the Russian Wikipedia is the largest Wikipedia written in Cyrillic or in a script other than Latin script. In April 2016, the project had 3,377 active editors who made at least five edits in that month, ranking third behind the English and Spanish versions. Difficult issues are resolved through the Arbitration Committee, which handles content disputes, blocks users or prohibits certain users from editing articles on certain topics. Administrators are elected through a vote.
Administrators who have become inactive may lose their privileges by an Arbitration Committee decision. As of 1 June 2012, some of the biggest categories in the Russian Wikipedia are: 176,411 biographical articles. Although the Western name order is used in Russian, the Russian Wikipedia uses lexical order for all articles on non-fictional persons; this order has been traditionally used in major Russian language encyclopedias, like the Great Soviet Encyclopedia. 144,322 human settlements articles. 28,187 river articles 19,302 film articles 16,925 animal articles 16,517 scientific articles 16,133 surname articles 13,936 footballers' articles 11,247 Musicians' articles 10,755 Writers' articles 9,243 album articles 9,237 articles on recipients of the Order of Lenin 7,307 Company's articles 6,734 plant articles 6,574 street articles 6,265 NGC astronomical articles 6,157 actors articles 5,719 artist articles 5,580 music group articles 5,292 Hero of the Soviet Union articles10,340 articles contain material from the Brockhaus and Efron Encyclopedic Dictionary.
More than 11,000 articles were translated from the English Wikipedia. In addition to common Wikipedia namespaces, the Russian Wikipedia has three custom ones: "Incubator" –, used as a training camp for new users and their first articles, "Project" – for Wikipedia projects and "Arbitration" – for arbitration requests. In 2015, Roman Leibov, a professor at University of Tartu, in an interview opined that articles related to humanities in the Russian Wikipedia are of inferior quality compared to English Wikipedia, some articles deteriorate with time, he suggested that this effect is due to overzealous policing of intellectual property rights by the community and bemoaned poor editing skills of some Wikipedians. The main page was created on 7 November 2002. On 30 December 2004, the 10,000th article was created. On 23 December 2005, the 50,000th article was created. On 16 August 2006, the 100,000th article was created. On 29 November 2006, the Russian Wikipedia received the National Runet Award in the Educational section.
On 10 March 2007, the 150,000th article was created. On 4 September 2007, the 200,000th article was created. On 27 November 2007, the Russian Wikipedia received the National Runet Award in the Educational section. On 17 March 2008, the 250,000th article was created. On 18 July 2008, the 300,000th article was created. On 22 January 2009, the 350,000th article was created. On 16 June 2009, the 400,000th article was created. On 25 November 2009, the Russian Wikipedia received the National Runet Award in the Science and Education section. On 25 February 2010, the 500,000th article was created. On 8 October 2010, the 600,000th article was created. On 12 April 2011, the 700,000th article was created. On 10 December 2011, the 800,000th article was created. On 8 September 2012, the 900,000th article was created. On 11 May 2013, the 1,000,000th article was created. On 27 March 2014, the 1,100,000th article was created. On 19 March 2015, the 1,200,000th article was created. On 29 March 2016, the 1,300,000th article was created.
On 1 October 2018, the 1,500,000th article was created. The Russian Wikipedia was created on 20 May 2001 in the first wave of non-English Wikipedias, along with editions in Catalan, Dutch, Esperanto, Hebrew, Japanese, Portuguese and Swedish; the first edit of the Russian Wikipedia was on 24 May 2001, consisted of the line "Россия – великая страна". The following edit changed it to the joke: "Россия — родина слонов" ("Russia is the motherland of elephants For a long time development was slow, but in the 12-month period between February 2005 and February 2006 it surpassed nine editions in other languages – the Catalan, Ukrainian, Finnish, Chinese and Danish Wikipedias. In 2006, 2007, 2009 and 2010 the Russian Wikipedia won the "Science and education" category of the "Runet Prize" award, supervised by the Russian government agency FAPMC. On 10 July 2012 Russian Wikipedia closed access to its content for 24 hours in protest against proposed amend
The Dutch Wikipedia is the Dutch-language edition of the free online encyclopedia, Wikipedia. It was started in June 2001; as of April 2019, the Dutch Wikipedia is the sixth-largest Wikipedia edition, with 1,963,438 articles. It was the fourth Wikipedia edition to exceed 1 million articles, after the English and French editions. In April 2016, 1154 active editors made at least five edits in that month; the Dutch Wikipedia was started on 19 June 2001, reached 100,000 articles on 14 October 2005. It surpassed the Polish Wikipedia as the sixth-largest edition of Wikipedia, but fell back to the eighth position. On 1 March 2006, it overtook the Swedish and Italian editions in one day to rise back to the sixth position; the edition's 500,000th article was created on 30 November 2008. In a 2006 Multiscope research study, the Dutch Wikipedia was rated the third-best Dutch-language website, after Google and Gmail, with a score of 8.1. The Dutch language Wikipedia has the largest ratio of Wikipedia pages per native speaker of all of the top 10 largest Wikipedia editions.
Its rate of daily article creations spiked in March 2006 growing to an average of 1,000 a day in early May 2006. After this number was reached, growth dropped to an average of only about 250 a day, comparable to the averages around December 2005. Since there have been more article-creation surges, one of the largest peaking at 2,000 new articles per day in September 2007, but the growth rate has always returned to the lowest average of around 250. In 2008, Dutch businessman Bob Sijthoff attempted to sue "the Vereniging Wikimedia Nederland" and "the Stichting Wikimedia Nederland" to force the removal of his Dutch Wikipedia article, which he stated contained "false and abusive" information. On December 10, 2008, the court rejected his request; the judge ruled that he had sued the wrong entity and that legal responsibility for the content of the articles would not lie in the Netherlands, but with the American Wikimedia Foundation. The majority of articles in Dutch Wikipedia were created by internet bots.
In October 2011, several bots created 80,000 articles in only 11 days. The Dutch Wikipedia's one-millionth article was created in December 2011, after another surge of bot activity saw 100,000 added articles in only 10 days. In late March 2013, the Dutch Wikipedia surpassed the French Wikipedia to become the third-largest edition of Wikipedia. In June 2013, it overtook the German Wikipedia to become the second-largest Wikipedia edition; the depth or editing depth of Wikipedia is a rough indicator of the encyclopedia's collaborative quality, showing how its articles are updated. The depth is measured by taking the average number of edits per article multiplied by the extent in which articles are supported by discussion. Among the nine language editions with one million articles, the Dutch and Polish Wikipedias in that order have depth parameters much lower than the other six; as of March 2012, for the English version the article depth is 666, for the German 88, for the French 153, for the Spanish 160, for the Dutch only 18.
Compared to most other Wikipedia editions with a similar number of articles, articles on the Dutch Wikipedia have less content with an average of 1,598 bytes per article. This is 40% of that of the French, Italian and Spanish editions. De Smits, Ap. "Dat zoeken we op! Wikipedia vs. de Britannica en Encarta". Personal Computer Magazine. April 2008. Dutch Wikipedia Dutch Wikipedia mobile version
Belgium the Kingdom of Belgium, is a country in Western Europe. It is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to the southwest, the North Sea to the northwest, it has a population of more than 11.4 million. The capital and largest city is Brussels; the sovereign state is a federal constitutional monarchy with a parliamentary system. Its institutional organisation is structured on both regional and linguistic grounds, it is divided into three autonomous regions: Flanders in the north, Wallonia in the south, the Brussels-Capital Region. Brussels is the smallest and most densely populated region, as well as the richest region in terms of GDP per capita. Belgium is home to two main linguistic groups or Communities: the Dutch-speaking Flemish Community, which constitutes about 59 percent of the population, the French-speaking Community, which comprises about 40 percent of all Belgians. A small German-speaking Community, numbering around one percent, exists in the East Cantons.
The Brussels-Capital Region is bilingual, although French is the dominant language. Belgium's linguistic diversity and related political conflicts are reflected in its political history and complex system of governance, made up of six different governments. Belgium was part of an area known as the Low Countries, a somewhat larger region than the current Benelux group of states that included parts of northern France and western Germany, its name is derived after the Roman province of Gallia Belgica. From the end of the Middle Ages until the 17th century, the area of Belgium was a prosperous and cosmopolitan centre of commerce and culture. Between the 16th and early 19th centuries, Belgium served as the battleground between many European powers, earning the moniker the "Battlefield of Europe", a reputation strengthened by both world wars; the country emerged in 1830 following the Belgian Revolution. Belgium participated in the Industrial Revolution and, during the course of the 20th century, possessed a number of colonies in Africa.
The second half of the 20th century was marked by rising tensions between the Dutch-speaking and the French-speaking citizens fueled by differences in language and culture and the unequal economic development of Flanders and Wallonia. This continuing antagonism has led to several far-reaching reforms, resulting in a transition from a unitary to a federal arrangement during the period from 1970 to 1993. Despite the reforms, tensions between the groups have remained, if not increased. Unemployment in Wallonia is more than double that of Flanders. Belgium is one of the six founding countries of the European Union and hosts the official seats of the European Commission, the Council of the European Union, the European Council, as well as a seat of the European Parliament in the country's capital, Brussels. Belgium is a founding member of the Eurozone, NATO, OECD, WTO, a part of the trilateral Benelux Union and the Schengen Area. Brussels hosts several of the EU's official seats as well as the headquarters of many major international organizations such as NATO.
Belgium is a developed country, with an advanced high-income economy. It has high standards of living, quality of life, education, is categorized as "very high" in the Human Development Index, it ranks as one of the safest or most peaceful countries in the world. The name "Belgium" is derived from Gallia Belgica, a Roman province in the northernmost part of Gaul that before Roman invasion in 100 BC, was inhabited by the Belgae, a mix of Celtic and Germanic peoples. A gradual immigration by Germanic Frankish tribes during the 5th century brought the area under the rule of the Merovingian kings. A gradual shift of power during the 8th century led the kingdom of the Franks to evolve into the Carolingian Empire; the Treaty of Verdun in 843 divided the region into Middle and West Francia and therefore into a set of more or less independent fiefdoms which, during the Middle Ages, were vassals either of the King of France or of the Holy Roman Emperor. Many of these fiefdoms were united in the Burgundian Netherlands of the 15th centuries.
Emperor Charles V extended the personal union of the Seventeen Provinces in the 1540s, making it far more than a personal union by the Pragmatic Sanction of 1549 and increased his influence over the Prince-Bishopric of Liège. The Eighty Years' War divided the Low Countries into the northern United Provinces and the Southern Netherlands; the latter were ruled successively by the Spanish and the Austrian Habsburgs and comprised most of modern Belgium. This was the theatre of most Franco-Spanish and Franco-Austrian wars during the 17th and 18th centuries. Following the campaigns of 1794 in the French Revolutionary Wars, the Low Countries—including territories that were never nominally under Habsburg rule, such as the Prince-Bishopric of Liège—were annexed by the French First Republic, ending Austrian rule in the region; the reunification of the Low Countries as the United Kingdom of the Netherlands occurred at the dissolution of the First French Empire in 1815, after the defeat of Napo
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
The Polish Wikipedia is the Polish-language edition of Wikipedia, a free online encyclopedia. Founded on September 26, 2001, it now has around 1,332,000 articles, making it the 10th-largest Wikipedia edition overall, it is the second-largest edition in a Slavic language, after the Russian Wikipedia. The Polish Wikipedia originated in September 2001 as an independent project under the domain wiki.rozeta.com.pl. At the suggestion of the founders of the English Wikipedia, the site was incorporated into the international project as http://pl.wikipedia.com on January 12, 2002, as http://pl.wikipedia.org on November 22 that year. To avoid domain squatting that could frustrate potential users, the Polish Wikipedia has its own domain, wikipedia.pl, which redirects to pl.wikipedia.org. On January 27, 2005 the founders of the Polish Wikipedia, Krzysztof P. Jasiutowicz and Paweł Jochym, received the Internet Citizen of the Year 2004 award issued by the Internet Obywatelski society. In July 2005, the tsca.bot bot program was instructed to upload statistics from official government pages about French and Italian municipalities to the Polish Wikipedia.
In a few months, the bot uploaded more than 40,000 articles. On October 13, 2009 the Polish Wikipedia received a "special recognition for social innovation" at the 2009 Jan Łukasiewicz Award ceremony, which recognises the most innovative Polish IT companies; the Polish Wikipedia exceeded 1,000,000 articles on September 24, 2013. In April 2016, the project had 1,140 active editors; the text of the Polish Wikipedia was first published on a DVD together with the paper edition of the magazine Enter SPECIAL in August 2005. The publisher did not make any attempt to contact the Wikimedia Foundation prior to making the DVD available on the market, the edition itself turned out to be illegal, as it violated the GNU FDL license. Additionally, the software used on the DVD worked improperly on Microsoft Windows 98. A second DVD edition was prepared as a joint project of Wikimedia Polska and the Polish publisher Helion, it contained articles written before June 4, 2006. The edition was completed on November 24, 2006, released at the end of July 2007 with a purchase price of 39 zlotys.
Polish Wikipedia Polish Wikipedia mobile version
Unidentified flying object
An unidentified flying object is an object observed in the sky, not identified. Most UFOs are identified as conventional objects or phenomena; the term is used for claimed observations of extraterrestrial spacecraft. The term "UFO" was coined in 1953 by the United States Air Force to serve as a catch-all for all such reports. In its initial definition, the USAF stated that a "UFOB" was "any airborne object which by performance, aerodynamic characteristics, or unusual features, does not conform to any presently known aircraft or missile type, or which cannot be positively identified as a familiar object." Accordingly, the term was restricted to that fraction of cases which remained unidentified after investigation, as the USAF was interested in potential national security reasons and/or "technical aspects". During the late 1940s and through the 1950s, UFOs were referred to popularly as "flying saucers" or "flying discs"; the term UFO became more widespread during the 1950s, at first in technical literature, but in popular use.
UFOs garnered considerable interest during the Cold War, an era associated with a heightened concern for national security, more in the 2010s, for unexplained reasons. Various studies have concluded that the phenomenon does not represent a threat to national security, nor does it contain anything worthy of scientific pursuit; the Oxford English Dictionary defines a UFO. The first published book to use the word was authored by Donald E. Keyhoe; the acronym "UFO" was coined by Captain Edward J. Ruppelt, who headed Project Blue Book the USAF's official investigation of UFOs, he wrote, "Obviously the term'flying saucer' is misleading when applied to objects of every conceivable shape and performance. For this reason the military prefers the more general, if less colorful, name: unidentified flying objects. UFO for short." Other phrases that were used and that predate the UFO acronym include "flying flapjack", "flying disc", "unexplained flying discs", "unidentifiable object". The phrase "flying saucer" had gained widespread attention after the summer of 1947.
On June 24, a civilian pilot named Kenneth Arnold reported seeing nine objects flying in formation near Mount Rainier. Arnold estimated the speed of discs to be over 1,200 mph. At the time, he claimed he described the objects flying in a saucer-like fashion, leading to newspaper accounts of "flying saucers" and "flying discs". Ufo's were referred to colloquially, as a "Bogey" by military personal and pilots during the cold war; the term "bogey" was used to report anomalies in radar blips, to indicate possible hostile forces that might be roaming in the area. In popular usage, the term UFO came to be used to refer to claims of alien spacecraft, because of the public and media ridicule associated with the topic, some ufologists and investigators prefer to use terms such as "unidentified aerial phenomenon" or "anomalous phenomena", as in the title of the National Aviation Reporting Center on Anomalous Phenomena. "Anomalous aerial vehicle" or "unidentified aerial system" are sometimes used in a military aviation context to describe unidentified targets.
Studies have established that the majority of UFO observations are misidentified conventional objects or natural phenomena—most aircraft, noctilucent clouds, nacreous clouds, or astronomical objects such as meteors or bright planets with a small percentage being hoaxes. Between 5% and 20% of reported sightings are not explained, therefore can be classified as unidentified in the strictest sense. While proponents of the extraterrestrial hypothesis suggest that these unexplained reports are of alien spacecraft, the null hypothesis cannot be excluded that these reports are other more prosaic phenomena that cannot be identified due to lack of complete information or due to the necessary subjectivity of the reports. Instead of accepting the null hypothesis, UFO enthusiasts tend to engage in special pleading by offering outlandish, untested explanations for the validity of the ETH; these violate Occam's razor. No scientific papers about UFOs have been published in peer-reviewed journals. There was, in the past, some debate in the scientific community about whether any scientific investigation into UFO sightings is warranted with the general conclusion being that the phenomenon was not worthy of serious investigation except as a cultural artifact.
UFOs have been the subject of investigations by various governments who have provided extensive records related to the subject. Many of the most involved government-sponsored investigations ended after agencies concluded that there was no benefit to continued investigation; the void left by the lack of institutional or scientific study has given rise to independent researchers and fringe groups, including the National Investigations Committee on Aerial Phenomena in the mid-20th century and, more the Mutual UFO Network and the Center for UFO Studies. The term "Ufology" is used to describe the collective efforts of those who study reports and associated evidence of unidentified flying objects. UFOs have become a prevalent theme in modern culture, the social phenomena have been the subject of academic research in sociology and psychology. Unexplained aerial observations have been reported throughout history; some were undoubtedly astronomical in nature: comets, bright meteors, one or more of the five planets that can be readily