Digital terrestrial television
Digital terrestrial television is a technology for broadcast television in which land-based television stations broadcast television content by radio waves to televisions in consumers' residences in a digital format. DTTV is a major technological advance over the previous analog television, has replaced analog, in common use since the middle of the 20th century. Test broadcasts began in 1998 with the changeover to DTTV beginning in 2006 and is now complete in many countries; the advantages of digital terrestrial television are similar to those obtained by digitising platforms such as cable TV, telecommunications: more efficient use of limited radio spectrum bandwidth, provision of more television channels than analog, better quality images, lower operating costs for broadcasters. Different countries have adopted different digital broadcasting standards; the amount of data that can be transmitted is directly affected by channel capacity and the modulation method of the transmission. North America uses the ATSC standard with 8VSB modulation, which has similar characteristics to the vestigial sideband modulation used for analog television.
This provides more immunity to interference, but is not immune to multipath distortion and does not provide for single-frequency network operation. The modulation method in DVB-T is COFDM with either 16-state Quadrature Amplitude Modulation. In general, 64QAM is capable of transmitting a greater bit rate, but is more susceptible to interference. 16 and 64QAM constellations can be combined in a single multiplex, providing a controllable degradation for more important program streams. This is called hierarchical modulation. DVB-T are designed to work in single frequency networks. Developments in video compression have resulted in improvements on the original H.262 MPEG 2 codec, surpassed by H.264/MPEG-4 AVC and more H.265 HEVC. H.264 enables three high-definition television services to be coded into a 24 Mbit/s DVB-T European terrestrial transmission channel. DVB-T2 increases this channel capacity to 40 Mbit/s, allowing more services. DTTV is received either via a digital set-top box, TV gateway or more now an integrated tuner included with television sets, that decodes the signal received via a standard television antenna.
These devices now include digital video recorder functionality. However, due to frequency planning issues, an aerial capable of receiving a different channel group may be required if the DTTV multiplexes lie outside the reception capabilities of the installed aerial; this is quite common in the UK. Indoor aerials are more to be affected by these issues and need replacing. Main articles: List of digital television deployments by country, Digital television transition Afghanistan launched digital transmissions in Kabul using DVB-T2/MPEG-4 on Sunday, 31 August 2014. Test transmissions had commenced on 4 UHF channels at the start of June 2014. Transmitters were provided by GatesAir. Bangladesh had its first DTT service DVB-T2 / MPEG-4 on April 2016 launched by the GS Group; the service is called RealVU. It is done with partnership with Beximco. GS Group acts as a supplier and integrator of its in-house hardware and software solutions for the operator's functioning in accordance with the modern standards of digital television.
RealVu provides more than 100 TV channels in HD quality. The digital TV set-top boxes developed by GS Group offer such functions as PVR and time-shift, along with an EPG. India adopted DVB-T system for digital television in July 1999; the first DVB-T transmission was started on 26 January 2003 in the four major metropolitan cities by Doordarshan. The terrestrial transmission is available in both digital and analog formats. 4 high power DVB-T transmitters were set up in the top 4 cities, which were upgraded to DVB-T2 + MPEG4 and DVB-H standards. An additional 190 high power, 400 low power DVB-T2 transmitters have been approved for Tier I, II and III cities of the country by 2017; the Indian telecom regulator, TRAI, had recommended the I&B to allow private broadcast companies to use the DTT technology, in 2005. So far, the Indian I&B ministry only permits private broadcast companies to use satellite, cable and IPTV based systems; the government's broadcasting organisation Doordarshan had started the free TV service over DVB - T2 to the mobile phone users from February 25 onwards and extended to cover 16 cities including the four metros from April 5, 2016.
Israel started digital transmissions in MPEG-4 on Sunday, August 2, 2009, anal
Barack Obama citizenship conspiracy theories
During Barack Obama's campaign for president in 2008, throughout his presidency, afterwards, a number of conspiracy theories falsely asserted Obama was ineligible to be President of the United States because he was not a natural-born citizen of the U. S. as required by Article Two of the Constitution. Theories alleged that Obama's published birth certificate was a forgery—that his actual birthplace was not Hawaii but Kenya. Other theories alleged that Obama became a citizen of Indonesia in childhood, thereby losing his U. S. citizenship. Still others claimed that Obama was not a natural-born U. S. citizen. A number of political commentators have characterized these various claims as a racist reaction to Obama's status as the first African-American president of the United States; these claims were promoted by fringe theorists, some of whom sought court rulings either to declare Obama ineligible to take office, or granting access to various documents which they claimed would evidence such ineligibility.
Some political opponents in the Republican Party, have expressed skepticism about Obama's citizenship or been unwilling to acknowledge it. Theories have persisted despite Obama's pre-election release of his official Hawaiian birth certificate in 2008, confirmation by the Hawaii Department of Health based on the original documents, the April 2011 release of a certified copy of Obama's original Certificate of Live Birth, contemporaneous birth announcements published in Hawaii newspapers. Polls conducted in 2010 suggested that at least 25% of adult Americans said that they doubted Obama's U. S. birth, a May 2011 Gallup poll found that the percentage had fallen to 13% of American adults. The fall has been attributed to Obama's release of the long form in April 2011. People who express doubts about Obama's eligibility or reject details about his early life are informally called "birthers", a term that parallels the nickname "truthers" for adherents of 9/11 conspiracy theories; these conspiracy theorists reject at least some of the following facts about his early life: Barack Obama was born on August 4, 1961, at Kapi'olani Maternity & Gynecological Hospital in Honolulu, Hawaii, to Ann Dunham, from Wichita and her husband Barack Obama Sr. a Luo from Nyang'oma Kogelo, Nyanza Province, attending the University of Hawaii.
Birth notices for Barack Obama were published in The Honolulu Advertiser on August 13 and the Honolulu Star-Bulletin on August 14, 1961. Obama's father's immigration file clearly states Barack Obama was born in Hawaii. One of his high school teachers, acquainted with his mother at the time, remembered hearing about the day of his birth. Obama's parents were divorced in 1964, he attended kindergarten in 1966–1967 at Noelani Elementary School in Honolulu. In 1967, his mother married Indonesian student Lolo Soetoro, attending the University of Hawaii, the family moved to Jakarta, where Obama attended the Catholic St. Francis of Assisi School before transferring to State Elementary School Menteng 01, an elite Indonesian public school in Menteng; as a child in Indonesia, Obama was called "Barry", sometimes Barry Soetoro, reflecting his stepfather's surname, sometimes Barry Obama, using his father's surname. When he was ten years old, Obama returned to Honolulu to live with his maternal grandparents and Stanley Dunham, has resided continuously in the United States since 1971.
Conspiracy theories about Obama's religion appeared at least as early as his 2004 U. S. Senate campaign in a press release by Illinois political candidate Andy Martin, according to a Los Angeles Times editorial, as Internet rumors. From the start of March 2008, rumors that Obama was born in Kenya before being flown to Hawaii were spread on conservative websites, with the suggestion that this would disqualify Obama from the presidency. In April of that year, some supporters of Hillary Clinton circulated anonymous chain emails repeating the same rumor; these and numerous other chain e-mails during the subsequent presidential election circulated false rumors about Obama's origin and birth certificate. On June 9, 2008, Jim Geraghty of the conservative website National Review Online suggested that Obama release his birth certificate. Geraghty wrote that releasing his birth certificate could debunk several false rumors circulating on the Internet, namely: that his middle name was Muhammad rather than Hussein.
In August 2008, Philip J. Berg, a former member of the Democratic State Committee of Pennsylvania, brought an unsuccessful lawsuit against Obama, which alleged "that Obama was born in Mombasa, Kenya."In October 2008, an NPR article referred to "Kenyan-born Sen. Barack Obama." That month, anonymous e-mails circulated claiming that the Associated Press had reported Obama was "Kenyan-Born". The claims were based on an AP story that had appeared five years earlier in a Kenyan publication, The Standard; the rumor-checking website Snopes.com found that the headline and lead-in sentence describing Obama as born in Kenya and misspelling his first name had been added by the Kenyan n
Streaming media is multimedia, received by and presented to an end-user while being delivered by a provider. The verb "to stream" refers to the process of obtaining media in this manner. A client end-user can use their media player to start playing digital video or digital audio content before the entire file has been transmitted. Distinguishing delivery method from the media distributed applies to telecommunications networks, as most of the delivery systems are either inherently streaming or inherently non-streaming. For example, in the 1930s, elevator music was among the earliest popular music available as streaming media; the term "streaming media" can apply to media other than video and audio, such as live closed captioning, ticker tape, real-time text, which are all considered "streaming text". Live streaming is the delivery of Internet content in real-time much as live television broadcasts content over the airwaves via a television signal. Live internet streaming requires a form of source media, an encoder to digitize the content, a media publisher, a content delivery network to distribute and deliver the content.
Live streaming does not need to be recorded at the origination point, although it is. There are challenges with streaming content on the Internet. If the user does not have enough bandwidth in their Internet connection, they may experience stops, lags, or slow buffering of the content; some users may not be able to stream certain content due to not having compatible computer or software systems. Some popular streaming services include the video sharing website YouTube and Mixer, which live stream the playing of video games. Netflix and Amazon Video stream movies and TV shows, Spotify, Apple Music and TIDAL stream music. In the early 1920s, George O. Squier was granted patents for a system for the transmission and distribution of signals over electrical lines, the technical basis for what became Muzak, a technology streaming continuous music to commercial customers without the use of radio. Attempts to display media on computers date back to the earliest days of computing in the mid-20th century.
However, little progress was made for several decades due to the high cost and limited capabilities of computer hardware. From the late 1980s through the 1990s, consumer-grade personal computers became powerful enough to display various media; the primary technical issues related to streaming were having enough CPU power bus bandwidth to support the required data rates, creating low-latency interrupt paths in the operating system to prevent buffer underrun, enabling skip-free streaming of the content. However, computer networks were still limited in the mid-1990s, audio and video media were delivered over non-streaming channels, such as by downloading a digital file from a remote server and saving it to a local drive on the end user's computer or storing it as a digital file and playing it back from CD-ROMs. In 1991 the first commercial Ethernet Switch was introduced, which enabled more powerful computer networks leading to the first streaming video solutions used by schools and corporations such as expanding Bloomberg Television worldwide.
In the mid 1990s the World Wide Web was established, but streaming audio would not be practical until years later. During the late 1990s and early 2000s, users had increased access to computer networks the Internet. During the early 2000s, users had access to increased network bandwidth in the "last mile"; these technological improvements facilitated the streaming of audio and video content to computer users in their homes and workplaces. There was an increasing use of standard protocols and formats, such as TCP/IP, HTTP, HTML as the Internet became commercialized, which led to an infusion of investment into the sector; the band Severe Tire Damage was the first group to perform live on the Internet. On June 24, 1993, the band was playing a gig at Xerox PARC while elsewhere in the building, scientists were discussing new technology for broadcasting on the Internet using multicasting; as proof of PARC's technology, the band's performance was broadcast and could be seen live in Australia and elsewhere.
In a March 2017 interview, band member Russ Haines stated that the band had used "half of the total bandwidth of the internet" to stream the performance, a 152-by-76 pixel video, updated eight to twelve times per second, with audio quality, "at best, a bad telephone connection". Microsoft Research developed a Microsoft TV application, compiled under MS Windows Studio Suite and tested in conjunction with Connectix QuickCam. RealNetworks was a pioneer in the streaming media markets, when it broadcast a baseball game between the New York Yankees and the Seattle Mariners over the Internet in 1995; the first symphonic concert on the Internet took place at the Paramount Theater in Seattle, Washington on November 10, 1995. The concert was a collaboration between The Seattle Symphony and various guest musicians such as Slash, Matt Cameron, Barrett Martin; when Word Magazine launched in 1995, they featured the first-ever streaming soundtracks on the Internet. Metro
9/11 conspiracy theories
There are many conspiracy theories that attribute the planning and execution of the September 11 attacks against the United States to parties other than, or in addition to, al-Qaeda including that there was advance knowledge of the attacks among high-level government officials. Government investigations and independent reviews have rejected these theories. Proponents of these theories assert that there are inconsistencies in the accepted version, or evidence, either ignored or overlooked; the most prominent conspiracy theory is that the collapse of the Twin Towers and 7 World Trade Center were the result of controlled demolitions rather than structural failure due to impact and fire. Another prominent belief is that the Pentagon was hit by a missile launched by elements from inside the U. S. government or that a commercial airliner was allowed to do so via an effective stand-down of the American military. Possible motives claimed by conspiracy theorists for such actions include justifying the invasions of Afghanistan and Iraq to advance their geostrategic interests, such as plans to construct a natural gas pipeline through Afghanistan.
Other conspiracy theories revolve around authorities having advance knowledge of the attacks and deliberately ignoring or assisting the attackers. The National Institute of Standards and Technology and the technology magazine Popular Mechanics have investigated and rejected the claims made by 9/11 conspiracy theorists; the 9/11 Commission and most of the civil engineering community accept that the impacts of jet aircraft at high speeds in combination with subsequent fires, not controlled demolition, led to the collapse of the Twin Towers, but some groups disagree with the arguments made by NIST and Popular Mechanics, including Architects & Engineers for 9/11 Truth. 9/11 conspiracy theorists reject one or both of the following facts about the 9/11 attacks: Al-Qaeda suicide operatives hijacked and crashed United Airlines Flight 175 and American Airlines Flight 11 into the twin towers of the World Trade Center, crashed American Airlines Flight 77 into the Pentagon. The impact and resulting fires caused the collapse of the Twin Towers and the destruction and damage of other buildings in the World Trade Center complex.
The Pentagon was damaged by the impact of the airliner and the resulting fire. The hijackers crashed a fourth plane into a field near Shanksville, Pennsylvania after the passengers and flight crew attempted to regain control of the aircraft. Pre-attack warnings of varying detail of the planned attacks against the United States by al-Qaeda were ignored due to a lack of communication between various law enforcement and intelligence personnel. For the lack of interagency communication, the 9/11 report cited bureaucratic inertia and laws passed in the 1970s to prevent abuses that caused scandals during that era, most notably the Watergate scandal; the report faulted both the Clinton and the Bush administrations with "failure of imagination."This consensus view is backed by various sources, including: The reports from government investigations – the 9/11 Commission Report, the studies into building performance carried out by the Federal Emergency Management Agency and the National Institute of Standards and Technology Investigations by non-government organizations that support the accepted account – such as those by scientists at Purdue University.
Articles supporting these facts and theories appearing in magazines such as Popular Mechanics, Scientific American, Time. Similar articles in news media throughout the World, including The Times of India, the Canadian Broadcasting Corporation, the BBC, Le Monde, Deutsche Welle, the Australian Broadcasting Corporation, The Chosun Ilbo of South Korea. Since the attacks, a variety of conspiracy theories have been put forward in Web sites and films. Many groups and individuals advocating 9/11 conspiracy theories identify as part of the 9/11 Truth movement. Within six hours of the attack, a suggestion appeared on an Internet chat room suggesting that the collapse of the towers looked like an act of controlled demolition. "If, in a few days, not one official has mentioned anything about the controlled demolition part," the author wrote, "I think we have a REALLY serious problem." The first theories that emerged focused on various perceived anomalies in the publicly available evidence, proponents developed more specific theories about an alleged plot.
One false allegation, circulated by e-mail and on the Web is that not a single Jew had been killed in the attack and that therefore the attacks must have been the work of the Mossad, not Islamic terrorists. Similar e-mail narratives claimed that all Arab taxi drivers were absent in downtown Manhattan that morning; the first elaborated theories appeared in Europe. One week after the attacks, the "inside job" theory was the subject of a thesis by a researcher from the French National Centre for Scientific Research published in Le Monde. Other theories sprang from the far corners of the globe within weeks. Six months after the attacks, Thierry Meyssan's piece on 9/11, L'Effroyable Imposture, topped the French bestseller list, its publication in English received little attention, but it remains one of the principal sources for "trutherism". 2003 saw the publication of The CIA and September 11 by former German state minister Andreas von Bülow and Operation 9/11 by the German journalist Gerhard Wisnewski.
While these th
Death of Osama bin Laden
Osama bin Laden, the founder and first leader of the Islamist group Al-Qaeda, was killed in Pakistan on May 2, 2011, shortly after 1:00 am PKT by United States Navy SEALs of the U. S. Naval Special Warfare Development Group; the operation, code-named Operation Neptune Spear, was carried out in a CIA-led operation with Joint Special Operations Command known as JSOC, coordinating the Special Mission Units involved in the raid. In addition to SEAL Team Six, participating units under JSOC included the 160th Special Operations Aviation Regiment —also known as "Night Stalkers"—and operators from the CIA's Special Activities Division, which recruits from former JSOC Special Mission Units; the operation ended a nearly 10-year search for bin Laden, following his role in the September 11 attacks on the United States. The raid on bin Laden's compound in Abbottabad, Pakistan was launched from Afghanistan. U. S. military officials said that after the raid U. S. forces took bin Laden's body to Afghanistan for identification buried him at sea within 24 hours of his death in accordance with Islamic tradition.
Al-Qaeda confirmed the death on May 6 with posts made on militant websites, vowing to avenge the killing. Other Pakistani militant groups, including the Tehrik-i-Taliban Pakistan, vowed retaliation against the U. S. and against Pakistan for not preventing the operation. The raid was supported by over 90% of the American public, was welcomed by the United Nations, NATO, the European Union and a large number of governments, but was condemned by others, including two-thirds of the Pakistani public. Legal and ethical aspects of the killing, such as his not being taken alive despite being unarmed, were questioned by others, including Amnesty International. Controversial was the decision not to release any photographic or DNA evidence of bin Laden's death to the public. In the aftermath of the killing, Pakistani Prime Minister Yousaf Raza Gillani formed a commission under Senior Justice Javed Iqbal to investigate the circumstances surrounding the attack; the resulting Abbottabad Commission Report, which revealed Pakistani state military and intelligence authorities' "collective failure" that enabled bin Laden to hide in Pakistan for nine years, was leaked to Al Jazeera on July 8, 2013.
Accounts of how bin Laden was located by U. S. intelligence differ. The White House and CIA director John Brennan stated that the process began with a fragment of information unearthed in 2002, resulting in years of investigation; this account states that by September 2010, these leads followed a courier to the Abbottabad compound, where the U. S. began intensive multiplatform surveillance. According to journalist Seymour Hersh and NBC News, the U. S. was tipped off about bin Laden's location by a Pakistani intelligence officer who offered details of where the Pakistani Intelligence Service held him in detention in exchange for a bounty. In August 2010, a former Pakistani intelligence officer approached the U. S. embassy station chief in Islamabad and offered to reveal bin Laden's location, in return for the $25 million reward, according to a retired senior U. S. intelligence official. This story was corroborated by two U. S. intelligence officials speaking to NBC News, had been reported by intelligence analyst Raelynn Hillhouse.
The Pakistani official informed U. S. intelligence that bin Laden had been located by Pakistani ISI in 2006, held under house arrest near Pakistani intelligence and military centers since. The official passed polygraph tests, after which the U. S. began local and satellite surveillance of bin Laden's Abbottabad residence. According to the retired senior U. S. intelligence official speaking to Hersh, bin Laden was ill at this point, financially supported by some within Saudi Arabia, kept by the ISI to better manage their complex relationship with Pakistani and Afghan Islamist groups. According to the official, retired CIA officials emphasized the importance of bin Laden's courier to the press, because they were nervous over torture scrutiny and possible prosecution. In May 2015 the German newspaper Bild am Sonntag reported that Germany's Federal Intelligence Service was aware that bin Laden was in Pakistan with the knowledge of Pakistani intelligence services; the BND informed the CIA that bin Laden was in Pakistan and Bild am Sonntag states that the CIA found his "precise location" through a courier.
Der Spiegel questioned the veracity of the report, produced in the midst of a scandal over BND and NSA collaboration. According to the earlier official version of his identification from a U. S. official, identification of al-Qaeda couriers was an early priority for interrogators at CIA black sites and the Guantanamo Bay detention camp, because bin Laden was believed to communicate through such couriers while concealing his whereabouts from al-Qaeda foot soldiers and top commanders. Bin Laden was known not to use phones after 1998, when the U. S. had launched missile strikes against his bases in Afghanistan in August by tracking an associate's satellite phone. The U. S. official had stated that by 2002, interrogators had heard uncorroborated claims about an al-Qaeda courier with the kunya Abu Ahmed al-Kuwaiti. One of those claims came from Mohammed al-Qahtani, a detainee interrogated for 48 days more or less continuously between November 23, 2002, January 11, 2003. At some point during this period, al-Qahtani told interrogators about a man known as Abu Ahmed al-Kuwaiti, part of the inner circle of al-Qaeda.
In 2003, Khalid Sheikh Mohammed, the alleged operational chief of al-Qaeda, stated that he was acquainted with al-Kuwaiti, but that the man was not active in al-Qaeda, according to a U. S. official. According to a
Washington, D. C. formally the District of Columbia and referred to as Washington or D. C. is the capital of the United States. Founded after the American Revolution as the seat of government of the newly independent country, Washington was named after George Washington, first President of the United States and Founding Father; as the seat of the United States federal government and several international organizations, Washington is an important world political capital. The city is one of the most visited cities in the world, with more than 20 million tourists annually; the signing of the Residence Act on July 16, 1790, approved the creation of a capital district located along the Potomac River on the country's East Coast. The U. S. Constitution provided for a federal district under the exclusive jurisdiction of the U. S. Congress, the District is therefore not a part of any state; the states of Maryland and Virginia each donated land to form the federal district, which included the pre-existing settlements of Georgetown and Alexandria.
The City of Washington was founded in 1791 to serve as the new national capital. In 1846, Congress returned the land ceded by Virginia. Washington had an estimated population of 702,455 as of July 2018, making it the 20th most populous city in the United States. Commuters from the surrounding Maryland and Virginia suburbs raise the city's daytime population to more than one million during the workweek. Washington's metropolitan area, the country's sixth largest, had a 2017 estimated population of 6.2 million residents. All three branches of the U. S. federal government are centered in the District: Congress and the U. S. Supreme Court. Washington is home to many national monuments, museums situated on or around the National Mall; the city hosts 177 foreign embassies as well as the headquarters of many international organizations, trade unions, non-profit, lobbying groups, professional associations, including the World Bank Group, the International Monetary Fund, the Organization of American States, AARP, the National Geographic Society, the Human Rights Campaign, the International Finance Corporation, the American Red Cross.
A locally elected mayor and a 13‑member council have governed the District since 1973. However, Congress may overturn local laws. D. C. residents elect a non-voting, at-large congressional delegate to the House of Representatives, but the District has no representation in the Senate. The District receives three electoral votes in presidential elections as permitted by the Twenty-third Amendment to the United States Constitution, ratified in 1961. Various tribes of the Algonquian-speaking Piscataway people inhabited the lands around the Potomac River when Europeans first visited the area in the early 17th century. One group known as the Nacotchtank maintained settlements around the Anacostia River within the present-day District of Columbia. Conflicts with European colonists and neighboring tribes forced the relocation of the Piscataway people, some of whom established a new settlement in 1699 near Point of Rocks, Maryland. In his Federalist No. 43, published January 23, 1788, James Madison argued that the new federal government would need authority over a national capital to provide for its own maintenance and safety.
Five years earlier, a band of unpaid soldiers besieged Congress while its members were meeting in Philadelphia. Known as the Pennsylvania Mutiny of 1783, the event emphasized the need for the national government not to rely on any state for its own security. Article One, Section Eight, of the Constitution permits the establishment of a "District as may, by cession of particular states, the acceptance of Congress, become the seat of the government of the United States". However, the Constitution does not specify a location for the capital. In what is now known as the Compromise of 1790, Alexander Hamilton, Thomas Jefferson came to an agreement that the federal government would pay each state's remaining Revolutionary War debts in exchange for establishing the new national capital in the southern United States. On July 9, 1790, Congress passed the Residence Act, which approved the creation of a national capital on the Potomac River; the exact location was to be selected by President George Washington, who signed the bill into law on July 16.
Formed from land donated by the states of Maryland and Virginia, the initial shape of the federal district was a square measuring 10 miles on each side, totaling 100 square miles. Two pre-existing settlements were included in the territory: the port of Georgetown, founded in 1751, the city of Alexandria, founded in 1749. During 1791–92, Andrew Ellicott and several assistants, including a free African American astronomer named Benjamin Banneker, surveyed the borders of the federal district and placed boundary stones at every mile point. Many of the stones are still standing. A new federal city was constructed on the north bank of the Potomac, to the east of Georgetown. On September 9, 1791, the three commissioners overseeing the capital's construction named the city in honor of President Washington; the federal district was named Columbia, a poetic name for the United States in use at that time. Congress held its first session in Washington on November 17, 1800. Congress passed the District of Columbia Organic Act of 1801 that organized the District and placed the entire territory under the exclusive control of the federal
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