Lions are said to inhabit the mountains of the Gash-Barka Region. There is also a small population of elephants that roam in some parts of the country. Dik-diks can also be found in many areas. The endangered African wild ass can be seen in Denakalia Region. Other local wildlife include bushbucks, duikers, greater kudus, klipspringers, African leopards, oryxs and crocodiles., The spotted hyena is widespread and fairly common. Between 1955 and 2001 there were no reported sightings of elephant herds, and they are thought to have fallen victim to the war of independence. In December 2001 a herd of about 30, including 10 juveniles, was observed in the vicinity of the Gash River. The elephants seemed to have formed a symbiotic relationship with olive baboons, with the baboons using the water holes dug by the elephants, while the elephants use the tree-top baboons as an early warning system.


Eritrea can be split into three ecoregions. To the east of the highlands are the hot, arid coastal plains stretching down to the southeast of the country. The cooler, more fertile highlands, reaching up to 3000m has a different habitat. Habitats here vary from the sub-tropical rainforest at Filfil Solomona to the precipitous cliffs and canyons of the southern highlands. The Afar Triangle or Danakil Depression of Eritrea is the probable location of a triple junction where three tectonic plates are pulling away from one another.The highest point of the country, Emba Soira, is located in the center of Eritrea, at 3,018 meters (9,902 ft) above sea level.


It is estimated that there are around 100 elephants left in Eritrea, the most northerly of East Africa's elephants. The endangered African wild dog (Lycaon pictus) was previously found in Eritrea, but is now deemed extirpated from the entire country. In Gash Barka, deadly snakes like saw-scaled viper are common. Puff adder and red spitting cobra are widespread and can be found even in the highlands.In the coastal areas marine species that are common include dolphin, dugong, whale shark, turtles, marlin/swordfish, and manta ray.


Eritrea is a one-party state in which national legislative elections have been repeatedly postponed. According to Human Rights Watch, the government's human rights record is considered among the worst in the world. Most Western countries have accused the Eritrean authorities of arbitrary arrest and detentions, and of detaining an unknown number of people without charge for their political activism. However, the Eritrean government has continually dismissed the accusations as politically motivated. In June 2015, a 500-page United Nations Human Rights Council report accused Eritrea's government of extrajudicial executions, torture, indefinitely prolonged national service and forced labour, and indicated that sexual harassment, rape and sexual servitude by state officials are also widespread.


In an attempt at reform, Eritrean government officials and NGO representatives have participated in numerous public meetings and dialogues. In these sessions they have answered questions as fundamental as, "What are human rights?", "Who determines what are human rights?", and "What should take precedence, human or communal rights?" In 2007, the Eritrean government also banned female genital mutilation. In Regional Assemblies and religious circles, Eritreans themselves speak out continuously against the use of female circumcision. They cite health concerns and individual freedom as being of primary concern when they say this. Furthermore, they implore rural peoples to cast away this ancient cultural practice. Additionally, a new movement called Citizens for Democratic Rights in Eritrea aimed at bringing about dialogue between the government and opposition was formed in early 2009. The group consists of ordinary citizens and some people close to the government.


In its 2014 Press Freedom Index, Reporters Without Borders ranked the media environment in Eritrea at the very bottom of a list of 178 countries, just below totalitarian North Korea. According to the BBC, "Eritrea is the only African country to have no privately owned news media", and Reporters Without Borders said of the public media, "[they] do nothing but relay the regime's belligerent and ultra-nationalist discourse. ... Not a single [foreign correspondent] now lives in Asmara." The state-owned news agency censors news about external events. Independent media have been banned since 2001. In 2015, The Guardian published an opinion piece claiming,


Even during the war, Eritrea developed its transportation infrastructure by asphalting new roads, improving its ports, and repairing war-damaged roads and bridges as a part of the Warsay Yika'alo Program. The most significant of these projects was the construction of a coastal highway of more than 500 km connecting Massawa with Asseb, as well as the rehabilitation of the Eritrean Railway. The rail line has been restored between the port of Massawa and the capital Asmara, although services are sporadic. Steam locomotives are sometimes used for groups of enthusiasts.


Eritrea is a multilingual country. The nation has no official language, as the Constitution establishes the "equality of all Eritrean languages". However, Tigrinya serves as the de facto language of national identity. With 2,540,000 total speakers of a population of 5,254,000 in 2006, Tigrinya is the most widely spoken language, particularly in the southern and central parts of Eritrea. Modern Standard Arabic and English serve as de facto working languages, with the latter used in university education and many technical fields. Italian, the former colonial language, is widely used in commerce and is taught as a second language in schools, with a few elderly monolinguals.


Eritrea has achieved significant improvements in health care and is one of the few countries to be on target to meet its Millennium Development Goal (MDG) targets in health, in particular child health. Life expectancy at birth has increased from 39.1 in 1960 to 59.5 years in 2008, maternal and child mortality rates have dropped dramatically and the health infrastructure has been expanded. Due to Eritrea's relative isolation, information and resources are extremely limited and according to the World Health Organisation (WHO) found in 2008 average life expectancy to be slightly less than 63 years. Immunisation and child nutrition has been tackled by working closely with schools in a multi-sectoral approach; the number of children vaccinated against measles almost doubled in seven years, from 40.7% to 78.5% and the underweight prevalence among children decreased by 12% in 1995–2002 (severe underweight prevalence by 28%). The National Malaria Protection Unit of the Ministry of Health has registered tremendous improvements in reducing malarial mortality by as much as 85% and the number of cases by 92% between 1998 and 2006. The Eritrean government has banned female genital mutilation (FGM), saying the practice was painful and put women at risk of life-threatening health problems.


Additionally, owing to its colonial history, cuisine in Eritrea features more Italian influences than are present in Ethiopian cooking, including more pasta and greater use of curry powders and cumin.The Italian Eritrean cuisine started to be practiced during the colonial times of the Kingdom of Italy, when a large number of Italians moved to Eritrea. They brought the use of "pasta" to Italian Eritrea, and it is one of the main food eaten in present-day Asmara. An Italian Eritrean cuisine emerged, and dishes common dishes are 'Pasta al Sugo e Berbere', which means "Pasta with tomato sauce and berbere" (spice), but there are many more like "lasagna" and "cotoletta alla milanese" (milano cutlet). Alongside sowa, people in Eritrea also tend to drink coffee. Mies is another popular local alcoholic beverage, made out of honey.


The culture of Eritrea has been largely shaped by the country's location on the Red Sea coast. One of the most recognizable parts of Eritrean culture is the coffee ceremony. Coffee (Ge'ez ቡን būn) is offered when visiting friends, during festivities, or as a daily staple of life. During the coffee ceremony, there are traditions that are upheld. The coffee is served in three rounds: the first brew or round is called awel in Tigrinya meaning first, the second round is called kalaay meaning second, and the third round is called bereka meaning "to be blessed". If coffee is politely declined, then most likely tea ("shai" ሻሂ shahee) will instead be served.


Eritrea (/ˌɛrᵻˈtreɪ.ə/ or /ˌɛrᵻˈtriːə/;, officially the State of Eritrea, is a country in East Africa. With its capital at Asmara, it is bordered by Sudan in the west, Ethiopia in the south, and Djibouti in the southeast. The northeastern and eastern parts of Eritrea have an extensive coastline along the Red Sea. The nation has a total area of approximately 117,600 km2 (45,406 sq mi), and includes the Dahlak Archipelago and several of the Hanish Islands. Its name Eritrea is based on the Greek name for the Red Sea (Ἐρυθρὰ Θάλασσα Erythra Thalassa), which was first adopted for Italian Eritrea in 1890.


Eritrea's ethnic groups each have their own styles of music and accompanying dances. Amongst the Tigrinya, the best known traditional musical genre is the guaila. Traditional instruments of Eritrean folk music include the stringed krar, kebero, begena, masenqo and the wata (a distant/rudimentary cousin of the violin). The most popular Eritrean artist is the Tigrinya singer Helen Meles, who is noted for her powerful voice and wide singing range. Other prominent local musicians include the Kunama singer Dehab Faytinga, Ruth Abraha, Bereket Mengisteab, Yemane Baria, and the late Abraham Afewerki.


During the Middle Ages, the Eritrea region was known as Medri Bahri ("sea-land"). The name Eritrea is derived from the ancient Greek name for Red Sea (Ἐρυθρὰ Θάλασσα Erythra Thalassa, based on the adjective ἐρυθρός erythros "red"). It was first formally adopted in 1890, with the formation of Italian Eritrea (Colonia Eritrea). The territory became the Eritrea Governorate within Italian East Africa in 1936. Eritrea was annexed by Ethiopia in 1953 (nominally within a federation until 1962) and an Eritrean Liberation Front formed in 1960. Eritrea gained independence following the 1993 referendum, and the name of the new state was defined as State of Eritrea in the 1997 constitution.[citation needed]


In 2010, a genetic study was conducted on the mummified remains of baboons that were brought back as gifts from Punt by the ancient Egyptians. Led by a research team from the Egyptian Museum and the University of California, the scientists used oxygen isotope analysis to examine hairs from two baboon mummies that had been preserved in the British Museum. One of the baboons had distorted isotopic data, so the other's oxygen isotope values were compared to those of present-day baboon specimens from regions of interest. The researchers found that the mummies most closely matched modern baboon specimens in Eritrea and Ethiopia, which they suggested implied that Punt was likely a narrow region that included eastern Ethiopia and all of Eritrea.


After the decline of Aksum, the Eritrean highlands were under the domain of Bahr Negash ruled by the Bahr Negus. The area was then known as Ma'ikele Bahr ("between the seas/rivers," i.e. the land between the Red Sea and the Mereb river). It was later renamed under Emperor Zara Yaqob as the domain of the Bahr Negash, the Medri Bahri ("Sea land" in Tingrinya, although it included some areas like Shire on the other side of the Mereb, today in Ethiopia). With its capital at Debarwa, the state's main provinces were Hamasien, Serae and Akele Guzai.


In 1922, Benito Mussolini's rise to power in Italy brought profound changes to the colonial government in Italian Eritrea. After il Duce declared the birth of the Italian Empire in May 1936, Italian Eritrea (enlarged with northern Ethiopia's regions) and Italian Somaliland were merged with the just conquered Ethiopia in the new Italian East Africa (Africa Orientale Italiana) administrative territory. This Fascist period was characterized by imperial expansion in the name of a "new Roman Empire". Eritrea was chosen by the Italian government to be the industrial center of Italian East Africa.


When Emperor Haile Selassie unilaterally dissolved the Eritrean parliament and annexed the country in 1962, the Eritrean Liberation Front (ELF) waged an armed struggle for independence. The ensuing Eritrean War for Independence went on for 30 years against successive Ethiopian governments until 1991, when the Eritrean People's Liberation Front (EPLF), a successor of the ELF, defeated the Ethiopian forces in Eritrea and helped a coalition of Ethiopian rebel forces take control of the Ethiopian Capital Addis Ababa.


Disagreements following the war have resulted in stalemate punctuated by periods of elevated tension and renewed threats of war. The stalemate led the President of Eritrea to urge the UN to take action on Ethiopia with the Eleven Letters penned by the President to the United Nations Security Council. The situation has been further escalated by the continued efforts of the Eritrean and Ethiopian leaders in supporting opposition in one another's countries.[citation needed] In 2011, Ethiopia accused Eritrea of planting bombs at an African Union summit in Addis Ababa, which was later supported by a UN report. Eritrea denied the claims.


However, Eritrea still faces many challenges. Despite number of physicians increasing from only 0.2 in 1993 to 0.5 in 2004 per 1000 population, this is still very low. Malaria and tuberculosis are common in Eritrea. HIV prevalence among the 15–49 group exceeds 2%. The fertility rate is at about 5 births per woman. Maternal mortality dropped by more than half from 1995 to 2002, although the figure is still high. Similarly, between 1995 and 2002, the number of births attended by skilled health personnel has doubled but still is only 28.3%. A major cause of death in neonates is by severe infection. Per capita expenditure on health is low in Eritrea.


Traditional Eritrean attire is quite varied among the ethnic groups of Eritrea. In the larger cities, most people dress in Western casual dress such as jeans and shirts. In offices, both men and women often dress in suits. Traditional clothing for Christian Tigrinya-speaking highlanders consists of bright white gowns called zurias for the women, and long white shirts accompanied by white pants for the men. In Muslim communities in the Eritrean lowland, the women traditionally dress in brightly colored clothes. Only Rashaida women maintain a tradition of covering half of their faces, though they do not cover their hair.


Football and cycling are the most popular sports in Eritrea. In recent years, Eritrean athletes have also seen increasing success in the international arena. Zersenay Tadese, an Eritrean athlete, currently holds the world record in half marathon distance running. The Tour of Eritrea, a multi-stage international cycling event, is held annually throughout the country. The Eritrea national cycling team has experienced a lot of success, winning the continental cycling championship several years in a row. Six Eritrean riders have been signed to international cycling teams, including Natnael Berhane and Daniel Teklehaimanot. Berhane was named African Sportsman of the Year in 2013, ahead of footballers Yaya Touré and Didier Drogba, while Teklehaimanot became the first Eritrean to ride the Vuelta a España in 2012. In 2015 Teklehaimanot won the King of the Mountains classification in the Critérium du Dauphine. Teklehaimanot and fellow Eritrean Merhawi Kudus became the first black African riders to compete in the Tour de France when they were selected by the MTN–Qhubeka team for the 2015 edition of the race, where, on 9 July, Teklehaimanot became the first African rider to wear the polkadot jersey.


During the last interglacial period, the Red Sea coast of Eritrea was occupied by early anatomically modern humans. It is believed that the area was on the route out of Africa that some scholars suggest was used by early humans to colonize the rest of the Old World. In 1999, the Eritrean Research Project Team composed of Eritrean, Canadian, American, Dutch and French scientists discovered a Paleolithic site with stone and obsidian tools dated to over 125,000 years old near the Bay of Zula south of Massawa, along the Red Sea littoral. The tools are believed to have been used by early humans to harvest marine resources like clams and oysters.


At the end of the 16th century, the Aussa Sultanate was established in the Denkel lowlands of Eritrea. The polity had come into existence in 1577, when Muhammed Jasa moved his capital from Harar to Aussa (Asaita) with the split of the Adal Sultanate into Aussa and the Sultanate of Harar. At some point after 1672, Aussa declined in conjunction with Imam Umar Din bin Adam's recorded ascension to the throne. In 1734, the Afar leader Kedafu, head of the Mudaito clan, seized power and established the Mudaito Dynasty. This marked the start of a new and more sophisticated polity that would last into the colonial period.


In the vacuum that followed the 1889 death of Emperor Yohannes II, Gen. Oreste Baratieri occupied the highlands along the Eritrean coast and Italy proclaimed the establishment of the new colony of Italian Eritrea, a colony of the Kingdom of Italy. In the Treaty of Wuchale (It. Uccialli) signed the same year, King Menelik of Shewa, a southern Ethiopian kingdom, recognized the Italian occupation of his rivals' lands of Bogos, Hamasien, Akkele Guzay, and Serae in exchange for guarantees of financial assistance and continuing access to European arms and ammunition. His subsequent victory over his rival kings and enthronement as Emperor Menelek II (r. 1889–1913) made the treaty formally binding upon the entire territory.


In the 1950s, the Ethiopian feudal administration under Emperor Haile Selassie sought to annex Eritrea and Italian Somaliland. He laid claim to both territories in a letter to Franklin D. Roosevelt at the Paris Peace Conference and at the First Session of the United Nations. In the United Nations, the debate over the fate of the former Italian colonies continued. The British and Americans preferred to cede all of Eritrea except the Western province to the Ethiopians as a reward for their support during World War II. The Independence Bloc of Eritrean parties consistently requested from the UN General Assembly that a referendum be held immediately to settle the Eritrean question of sovereignty.


The Eritrean highway system is named according to the road classification. The three levels of classification are: primary (P), secondary (S), and tertiary (T). The lowest level road is tertiary and serves local interests. Typically they are improved earth roads which are occasionally paved. During the wet seasons these roads typically become impassable. The next higher level road is a secondary road and typically is a single-layered asphalt road that connects district capitals together and those to the regional capitals. Roads that are considered primary roads are those that are fully asphalted (throughout their entire length) and in general they carry traffic between all the major towns in Eritrea.


According to recent estimates, 50% of the population adheres to Christianity, Islam 48%, while 2% of the population follows other religions including traditional African religion and animism. According to a study made by Pew Research Center, 63% adheres to Christianity and 36% adheres to Islam. Since May 2002, the government of Eritrea has officially recognized the Eritrean Orthodox Tewahedo Church (Oriental Orthodox), Sunni Islam, the Eritrean Catholic Church (a Metropolitanate sui juris) and the Evangelical Lutheran church. All other faiths and denominations are required to undergo a registration process. Among other things, the government's registration system requires religious groups to submit personal information on their membership to be allowed to worship.


Education in Eritrea is officially compulsory between seven and 13 years of age. However, the education infrastructure is inadequate to meet current needs. Statistics vary at the elementary level, suggesting that between 65 and 70% of school-aged children attend primary school; Approximately 61% attend secondary school. Student-teacher ratios are high: 45 to 1 at the elementary level and 54 to 1 at the secondary level. There are an average 63 students per classroom at the elementary level and 97 per classroom at the secondary level. Learning hours at school are often less than six hours per day. Skill shortages are present at all levels of the education system, and funding for and access to education vary significantly by gender and location. Illiteracy estimates for Eritrea range from around 40% to as high as 70%.


A typical traditional Eritrean dish consists of injera accompanied by a spicy stew, which frequently includes beef, kid, lamb or fish. Overall, Eritrean cuisine strongly resembles those of neighboring Ethiopia, Eritrean cooking tend to feature more seafood than Ethiopian cuisine on account of their coastal location. Eritrean dishes are also frequently "lighter" in texture than Ethiopian meals. They likewise tend to employ less seasoned butter and spices and more tomatoes, as in the tsebhi dorho delicacy.


Depleted uranium is also used as a shielding material in some containers used to store and transport radioactive materials. While the metal itself is radioactive, its high density makes it more effective than lead in halting radiation from strong sources such as radium. Other uses of depleted uranium include counterweights for aircraft control surfaces, as ballast for missile re-entry vehicles and as a shielding material. Due to its high density, this material is found in inertial guidance systems and in gyroscopic compasses. Depleted uranium is preferred over similarly dense metals due to its ability to be easily machined and cast as well as its relatively low cost. The main risk of exposure to depleted uranium is chemical poisoning by uranium oxide rather than radioactivity (uranium being only a weak alpha emitter).


The discovery and isolation of radium in uranium ore (pitchblende) by Marie Curie sparked the development of uranium mining to extract the radium, which was used to make glow-in-the-dark paints for clock and aircraft dials. This left a prodigious quantity of uranium as a waste product, since it takes three tonnes of uranium to extract one gram of radium. This waste product was diverted to the glazing industry, making uranium glazes very inexpensive and abundant. Besides the pottery glazes, uranium tile glazes accounted for the bulk of the use, including common bathroom and kitchen tiles which can be produced in green, yellow, mauve, black, blue, red and other colors.


The X-10 Graphite Reactor at Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee, formerly known as the Clinton Pile and X-10 Pile, was the world's second artificial nuclear reactor (after Enrico Fermi's Chicago Pile) and was the first reactor designed and built for continuous operation. Argonne National Laboratory's Experimental Breeder Reactor I, located at the Atomic Energy Commission's National Reactor Testing Station near Arco, Idaho, became the first nuclear reactor to create electricity on 20 December 1951. Initially, four 150-watt light bulbs were lit by the reactor, but improvements eventually enabled it to power the whole facility (later, the town of Arco became the first in the world to have all its electricity come from nuclear power generated by BORAX-III, another reactor designed and operated by Argonne National Laboratory). The world's first commercial scale nuclear power station, Obninsk in the Soviet Union, began generation with its reactor AM-1 on 27 June 1954. Other early nuclear power plants were Calder Hall in England, which began generation on 17 October 1956, and the Shippingport Atomic Power Station in Pennsylvania, which began on 26 May 1958. Nuclear power was used for the first time for propulsion by a submarine, the USS Nautilus, in 1954.


Uranium is a naturally occurring element that can be found in low levels within all rock, soil, and water. Uranium is the 51st element in order of abundance in the Earth's crust. Uranium is also the highest-numbered element to be found naturally in significant quantities on Earth and is almost always found combined with other elements. Along with all elements having atomic weights higher than that of iron, it is only naturally formed in supernovae. The decay of uranium, thorium, and potassium-40 in the Earth's mantle is thought to be the main source of heat that keeps the outer core liquid and drives mantle convection, which in turn drives plate tectonics.


Uranium-235 was the first isotope that was found to be fissile. Other naturally occurring isotopes are fissionable, but not fissile. On bombardment with slow neutrons, its uranium-235 isotope will most of the time divide into two smaller nuclei, releasing nuclear binding energy and more neutrons. If too many of these neutrons are absorbed by other uranium-235 nuclei, a nuclear chain reaction occurs that results in a burst of heat or (in special circumstances) an explosion. In a nuclear reactor, such a chain reaction is slowed and controlled by a neutron poison, absorbing some of the free neutrons. Such neutron absorbent materials are often part of reactor control rods (see nuclear reactor physics for a description of this process of reactor control).


In nature, uranium(VI) forms highly soluble carbonate complexes at alkaline pH. This leads to an increase in mobility and availability of uranium to groundwater and soil from nuclear wastes which leads to health hazards. However, it is difficult to precipitate uranium as phosphate in the presence of excess carbonate at alkaline pH. A Sphingomonas sp. strain BSAR-1 has been found to express a high activity alkaline phosphatase (PhoK) that has been applied for bioprecipitation of uranium as uranyl phosphate species from alkaline solutions. The precipitation ability was enhanced by overexpressing PhoK protein in E. coli.


It is estimated that 5.5 million tonnes of uranium exists in ore reserves that are economically viable at US$59 per lb of uranium, while 35 million tonnes are classed as mineral resources (reasonable prospects for eventual economic extraction). Prices went from about $10/lb in May 2003 to $138/lb in July 2007. This has caused a big increase in spending on exploration, with US$200 million being spent worldwide in 2005, a 54% increase on the previous year. This trend continued through 2006, when expenditure on exploration rocketed to over $774 million, an increase of over 250% compared to 2004. The OECD Nuclear Energy Agency said exploration figures for 2007 would likely match those for 2006.


A team led by Enrico Fermi in 1934 observed that bombarding uranium with neutrons produces the emission of beta rays (electrons or positrons from the elements produced; see beta particle). The fission products were at first mistaken for new elements of atomic numbers 93 and 94, which the Dean of the Faculty of Rome, Orso Mario Corbino, christened ausonium and hesperium, respectively. The experiments leading to the discovery of uranium's ability to fission (break apart) into lighter elements and release binding energy were conducted by Otto Hahn and Fritz Strassmann in Hahn's laboratory in Berlin. Lise Meitner and her nephew, the physicist Otto Robert Frisch, published the physical explanation in February 1939 and named the process "nuclear fission". Soon after, Fermi hypothesized that the fission of uranium might release enough neutrons to sustain a fission reaction. Confirmation of this hypothesis came in 1939, and later work found that on average about 2.5 neutrons are released by each fission of the rare uranium isotope uranium-235. Further work found that the far more common uranium-238 isotope can be transmuted into plutonium, which, like uranium-235, is also fissile by thermal neutrons. These discoveries led numerous countries to begin working on the development of nuclear weapons and nuclear power.


The interactions of carbonate anions with uranium(VI) cause the Pourbaix diagram to change greatly when the medium is changed from water to a carbonate containing solution. While the vast majority of carbonates are insoluble in water (students are often taught that all carbonates other than those of alkali metals are insoluble in water), uranium carbonates are often soluble in water. This is because a U(VI) cation is able to bind two terminal oxides and three or more carbonates to form anionic complexes.


Uranium is more plentiful than antimony, tin, cadmium, mercury, or silver, and it is about as abundant as arsenic or molybdenum. Uranium is found in hundreds of minerals, including uraninite (the most common uranium ore), carnotite, autunite, uranophane, torbernite, and coffinite. Significant concentrations of uranium occur in some substances such as phosphate rock deposits, and minerals such as lignite, and monazite sands in uranium-rich ores (it is recovered commercially from sources with as little as 0.1% uranium).


Natural uranium consists of three major isotopes: uranium-238 (99.28% natural abundance), uranium-235 (0.71%), and uranium-234 (0.0054%). All three are radioactive, emitting alpha particles, with the exception that all three of these isotopes have small probabilities of undergoing spontaneous fission, rather than alpha emission. There are also five other trace isotopes: uranium-239, which is formed when 238U undergoes spontaneous fission, releasing neutrons that are captured by another 238U atom; uranium-237, which is formed when 238U captures a neutron but emits two more, which then decays to neptunium-237; uranium-233, which is formed in the decay chain of that neptunium-237; and finally, uranium-236 and -240, which appear in the decay chain of primordial plutonium-244. It is also expected that thorium-232 should be able to undergo double beta decay, which would produce uranium-232, but this has not yet been observed experimentally.


An additional 4.6 billion tonnes of uranium are estimated to be in sea water (Japanese scientists in the 1980s showed that extraction of uranium from sea water using ion exchangers was technically feasible). There have been experiments to extract uranium from sea water, but the yield has been low due to the carbonate present in the water. In 2012, ORNL researchers announced the successful development of a new absorbent material dubbed HiCap which performs surface retention of solid or gas molecules, atoms or ions and also effectively removes toxic metals from water, according to results verified by researchers at Pacific Northwest National Laboratory.


Many contemporary uses of uranium exploit its unique nuclear properties. Uranium-235 has the distinction of being the only naturally occurring fissile isotope. Uranium-238 is fissionable by fast neutrons, and is fertile, meaning it can be transmuted to fissile plutonium-239 in a nuclear reactor. Another fissile isotope, uranium-233, can be produced from natural thorium and is also important in nuclear technology. While uranium-238 has a small probability for spontaneous fission or even induced fission with fast neutrons, uranium-235 and to a lesser degree uranium-233 have a much higher fission cross-section for slow neutrons. In sufficient concentration, these isotopes maintain a sustained nuclear chain reaction. This generates the heat in nuclear power reactors, and produces the fissile material for nuclear weapons. Depleted uranium (238U) is used in kinetic energy penetrators and armor plating.


A person can be exposed to uranium (or its radioactive daughters, such as radon) by inhaling dust in air or by ingesting contaminated water and food. The amount of uranium in air is usually very small; however, people who work in factories that process phosphate fertilizers, live near government facilities that made or tested nuclear weapons, live or work near a modern battlefield where depleted uranium weapons have been used, or live or work near a coal-fired power plant, facilities that mine or process uranium ore, or enrich uranium for reactor fuel, may have increased exposure to uranium. Houses or structures that are over uranium deposits (either natural or man-made slag deposits) may have an increased incidence of exposure to radon gas. The Occupational Safety and Health Administration (OSHA) has set the permissible exposure limit for uranium exposure in the workplace as 0.25 mg/m3 over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 0.2 mg/m3 over an 8-hour workday and a short-term limit of 0.6 mg/m3. At levels of 10 mg/m3, uranium is immediately dangerous to life and health.


The most common forms of uranium oxide are triuranium octoxide (U
3O
8) and UO
2. Both oxide forms are solids that have low solubility in water and are relatively stable over a wide range of environmental conditions. Triuranium octoxide is (depending on conditions) the most stable compound of uranium and is the form most commonly found in nature. Uranium dioxide is the form in which uranium is most commonly used as a nuclear reactor fuel. At ambient temperatures, UO
2 will gradually convert to U
3O
8. Because of their stability, uranium oxides are generally considered the preferred chemical form for storage or disposal.


The use of uranium in its natural oxide form dates back to at least the year 79 CE, when it was used to add a yellow color to ceramic glazes. Yellow glass with 1% uranium oxide was found in a Roman villa on Cape Posillipo in the Bay of Naples, Italy, by R. T. Gunther of the University of Oxford in 1912. Starting in the late Middle Ages, pitchblende was extracted from the Habsburg silver mines in Joachimsthal, Bohemia (now Jáchymov in the Czech Republic), and was used as a coloring agent in the local glassmaking industry. In the early 19th century, the world's only known sources of uranium ore were these mines.


On 2 December 1942, as part of the Manhattan Project, another team led by Enrico Fermi was able to initiate the first artificial self-sustained nuclear chain reaction, Chicago Pile-1. Working in a lab below the stands of Stagg Field at the University of Chicago, the team created the conditions needed for such a reaction by piling together 400 short tons (360 metric tons) of graphite, 58 short tons (53 metric tons) of uranium oxide, and six short tons (5.5 metric tons) of uranium metal, a majority of which was supplied by Westinghouse Lamp Plant in a makeshift production process.


Uranium is used as a colorant in uranium glass producing orange-red to lemon yellow hues. It was also used for tinting and shading in early photography. The 1789 discovery of uranium in the mineral pitchblende is credited to Martin Heinrich Klaproth, who named the new element after the planet Uranus. Eugène-Melchior Péligot was the first person to isolate the metal and its radioactive properties were discovered in 1896 by Henri Becquerel. Research by Otto Hahn, Lise Meitner, Enrico Fermi and others, such as J. Robert Oppenheimer starting in 1934 led to its use as a fuel in the nuclear power industry and in Little Boy, the first nuclear weapon used in war. An ensuing arms race during the Cold War between the United States and the Soviet Union produced tens of thousands of nuclear weapons that used uranium metal and uranium-derived plutonium-239. The security of those weapons and their fissile material following the breakup of the Soviet Union in 1991 is an ongoing concern for public health and safety. See Nuclear proliferation.


In nature, uranium is found as uranium-238 (99.2742%) and uranium-235 (0.7204%). Isotope separation concentrates (enriches) the fissionable uranium-235 for nuclear weapons and most nuclear power plants, except for gas cooled reactors and pressurised heavy water reactors. Most neutrons released by a fissioning atom of uranium-235 must impact other uranium-235 atoms to sustain the nuclear chain reaction. The concentration and amount of uranium-235 needed to achieve this is called a 'critical mass'.


The major application of uranium in the military sector is in high-density penetrators. This ammunition consists of depleted uranium (DU) alloyed with 1–2% other elements, such as titanium or molybdenum. At high impact speed, the density, hardness, and pyrophoricity of the projectile enable the destruction of heavily armored targets. Tank armor and other removable vehicle armor can also be hardened with depleted uranium plates. The use of depleted uranium became politically and environmentally contentious after the use of such munitions by the US, UK and other countries during wars in the Persian Gulf and the Balkans raised questions concerning uranium compounds left in the soil (see Gulf War Syndrome).


The discovery of the element is credited to the German chemist Martin Heinrich Klaproth. While he was working in his experimental laboratory in Berlin in 1789, Klaproth was able to precipitate a yellow compound (likely sodium diuranate) by dissolving pitchblende in nitric acid and neutralizing the solution with sodium hydroxide. Klaproth assumed the yellow substance was the oxide of a yet-undiscovered element and heated it with charcoal to obtain a black powder, which he thought was the newly discovered metal itself (in fact, that powder was an oxide of uranium). He named the newly discovered element after the planet Uranus, (named after the primordial Greek god of the sky), which had been discovered eight years earlier by William Herschel.


Uranium ore is mined in several ways: by open pit, underground, in-situ leaching, and borehole mining (see uranium mining). Low-grade uranium ore mined typically contains 0.01 to 0.25% uranium oxides. Extensive measures must be employed to extract the metal from its ore. High-grade ores found in Athabasca Basin deposits in Saskatchewan, Canada can contain up to 23% uranium oxides on average. Uranium ore is crushed and rendered into a fine powder and then leached with either an acid or alkali. The leachate is subjected to one of several sequences of precipitation, solvent extraction, and ion exchange. The resulting mixture, called yellowcake, contains at least 75% uranium oxides U3O8. Yellowcake is then calcined to remove impurities from the milling process before refining and conversion.


Two major types of atomic bombs were developed by the United States during World War II: a uranium-based device (codenamed "Little Boy") whose fissile material was highly enriched uranium, and a plutonium-based device (see Trinity test and "Fat Man") whose plutonium was derived from uranium-238. The uranium-based Little Boy device became the first nuclear weapon used in war when it was detonated over the Japanese city of Hiroshima on 6 August 1945. Exploding with a yield equivalent to 12,500 tonnes of TNT, the blast and thermal wave of the bomb destroyed nearly 50,000 buildings and killed approximately 75,000 people (see Atomic bombings of Hiroshima and Nagasaki). Initially it was believed that uranium was relatively rare, and that nuclear proliferation could be avoided by simply buying up all known uranium stocks, but within a decade large deposits of it were discovered in many places around the world.


In 2005, seventeen countries produced concentrated uranium oxides, with Canada (27.9% of world production) and Australia (22.8%) being the largest producers and Kazakhstan (10.5%), Russia (8.0%), Namibia (7.5%), Niger (7.4%), Uzbekistan (5.5%), the United States (2.5%), Argentina (2.1%), Ukraine (1.9%) and China (1.7%) also producing significant amounts. Kazakhstan continues to increase production and may have become the world's largest producer of uranium by 2009 with an expected production of 12,826 tonnes, compared to Canada with 11,100 t and Australia with 9,430 t. In the late 1960s, UN geologists also discovered major uranium deposits and other rare mineral reserves in Somalia. The find was the largest of its kind, with industry experts estimating the deposits at over 25% of the world's then known uranium reserves of 800,000 tons.


During the Cold War between the Soviet Union and the United States, huge stockpiles of uranium were amassed and tens of thousands of nuclear weapons were created using enriched uranium and plutonium made from uranium. Since the break-up of the Soviet Union in 1991, an estimated 600 short tons (540 metric tons) of highly enriched weapons grade uranium (enough to make 40,000 nuclear warheads) have been stored in often inadequately guarded facilities in the Russian Federation and several other former Soviet states. Police in Asia, Europe, and South America on at least 16 occasions from 1993 to 2005 have intercepted shipments of smuggled bomb-grade uranium or plutonium, most of which was from ex-Soviet sources. From 1993 to 2005 the Material Protection, Control, and Accounting Program, operated by the federal government of the United States, spent approximately US $550 million to help safeguard uranium and plutonium stockpiles in Russia. This money was used for improvements and security enhancements at research and storage facilities. Scientific American reported in February 2006 that in some of the facilities security consisted of chain link fences which were in severe states of disrepair. According to an interview from the article, one facility had been storing samples of enriched (weapons grade) uranium in a broom closet before the improvement project; another had been keeping track of its stock of nuclear warheads using index cards kept in a shoe box.


Salts of many oxidation states of uranium are water-soluble and may be studied in aqueous solutions. The most common ionic forms are U3+ (brown-red), U4+ (green), UO+
2 (unstable), and UO2+
2 (yellow), for U(III), U(IV), U(V), and U(VI), respectively. A few solid and semi-metallic compounds such as UO and US exist for the formal oxidation state uranium(II), but no simple ions are known to exist in solution for that state. Ions of U3+ liberate hydrogen from water and are therefore considered to be highly unstable. The UO2+
2 ion represents the uranium(VI) state and is known to form compounds such as uranyl carbonate, uranyl chloride and uranyl sulfate. UO2+
2 also forms complexes with various organic chelating agents, the most commonly encountered of which is uranyl acetate.


Some organisms, such as the lichen Trapelia involuta or microorganisms such as the bacterium Citrobacter, can absorb concentrations of uranium that are up to 300 times the level of their environment. Citrobacter species absorb uranyl ions when given glycerol phosphate (or other similar organic phosphates). After one day, one gram of bacteria can encrust themselves with nine grams of uranyl phosphate crystals; this creates the possibility that these organisms could be used in bioremediation to decontaminate uranium-polluted water. The proteobacterium Geobacter has also been shown to bioremediate uranium in ground water. The mycorrhizal fungus Glomus intraradices increases uranium content in the roots of its symbiotic plant.


Uranium metal heated to 250 to 300 °C (482 to 572 °F) reacts with hydrogen to form uranium hydride. Even higher temperatures will reversibly remove the hydrogen. This property makes uranium hydrides convenient starting materials to create reactive uranium powder along with various uranium carbide, nitride, and halide compounds. Two crystal modifications of uranium hydride exist: an α form that is obtained at low temperatures and a β form that is created when the formation temperature is above 250 °C.


Uranium carbides and uranium nitrides are both relatively inert semimetallic compounds that are minimally soluble in acids, react with water, and can ignite in air to form U
3O
8. Carbides of uranium include uranium monocarbide (UC), uranium dicarbide (UC
2), and diuranium tricarbide (U
2C
3). Both UC and UC
2 are formed by adding carbon to molten uranium or by exposing the metal to carbon monoxide at high temperatures. Stable below 1800 °C, U
2C
3 is prepared by subjecting a heated mixture of UC and UC
2 to mechanical stress. Uranium nitrides obtained by direct exposure of the metal to nitrogen include uranium mononitride (UN), uranium dinitride (UN
2), and diuranium trinitride (U
2N
3).


To be considered 'enriched', the uranium-235 fraction should be between 3% and 5%. This process produces huge quantities of uranium that is depleted of uranium-235 and with a correspondingly increased fraction of uranium-238, called depleted uranium or 'DU'. To be considered 'depleted', the uranium-235 isotope concentration should be no more than 0.3%. The price of uranium has risen since 2001, so enrichment tailings containing more than 0.35% uranium-235 are being considered for re-enrichment, driving the price of depleted uranium hexafluoride above $130 per kilogram in July 2007 from $5 in 2001.


Normal functioning of the kidney, brain, liver, heart, and other systems can be affected by uranium exposure, because, besides being weakly radioactive, uranium is a toxic metal. Uranium is also a reproductive toxicant. Radiological effects are generally local because alpha radiation, the primary form of 238U decay, has a very short range, and will not penetrate skin. Uranyl (UO2+
2) ions, such as from uranium trioxide or uranyl nitrate and other hexavalent uranium compounds, have been shown to cause birth defects and immune system damage in laboratory animals. While the CDC has published one study that no human cancer has been seen as a result of exposure to natural or depleted uranium, exposure to uranium and its decay products, especially radon, are widely known and significant health threats. Exposure to strontium-90, iodine-131, and other fission products is unrelated to uranium exposure, but may result from medical procedures or exposure to spent reactor fuel or fallout from nuclear weapons. Although accidental inhalation exposure to a high concentration of uranium hexafluoride has resulted in human fatalities, those deaths were associated with the generation of highly toxic hydrofluoric acid and uranyl fluoride rather than with uranium itself. Finely divided uranium metal presents a fire hazard because uranium is pyrophoric; small grains will ignite spontaneously in air at room temperature.


The gas centrifuge process, where gaseous uranium hexafluoride (UF
6) is separated by the difference in molecular weight between 235UF6 and 238UF6 using high-speed centrifuges, is the cheapest and leading enrichment process. The gaseous diffusion process had been the leading method for enrichment and was used in the Manhattan Project. In this process, uranium hexafluoride is repeatedly diffused through a silver-zinc membrane, and the different isotopes of uranium are separated by diffusion rate (since uranium 238 is heavier it diffuses slightly slower than uranium-235). The molecular laser isotope separation method employs a laser beam of precise energy to sever the bond between uranium-235 and fluorine. This leaves uranium-238 bonded to fluorine and allows uranium-235 metal to precipitate from the solution. An alternative laser method of enrichment is known as atomic vapor laser isotope separation (AVLIS) and employs visible tunable lasers such as dye lasers. Another method used is liquid thermal diffusion.


Uranium is a chemical element with symbol U and atomic number 92. It is a silvery-white metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weakly radioactive because all its isotopes are unstable (with half-lives of the six naturally known isotopes, uranium-233 to uranium-238, varying between 69 years and 4.5 billion years). The most common isotopes of uranium are uranium-238 (which has 146 neutrons and accounts for almost 99.3% of the uranium found in nature) and uranium-235 (which has 143 neutrons, accounting for 0.7% of the element found naturally). Uranium has the second highest atomic weight of the primordially occurring elements, lighter only than plutonium. Its density is about 70% higher than that of lead, but slightly lower than that of gold or tungsten. It occurs naturally in low concentrations of a few parts per million in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite.


Uranium metal reacts with almost all non-metal elements (with an exception of the noble gases) and their compounds, with reactivity increasing with temperature. Hydrochloric and nitric acids dissolve uranium, but non-oxidizing acids other than hydrochloric acid attack the element very slowly. When finely divided, it can react with cold water; in air, uranium metal becomes coated with a dark layer of uranium oxide. Uranium in ores is extracted chemically and converted into uranium dioxide or other chemical forms usable in industry.


During the later stages of World War II, the entire Cold War, and to a lesser extent afterwards, uranium-235 has been used as the fissile explosive material to produce nuclear weapons. Initially, two major types of fission bombs were built: a relatively simple device that uses uranium-235 and a more complicated mechanism that uses plutonium-239 derived from uranium-238. Later, a much more complicated and far more powerful type of fission/fusion bomb (thermonuclear weapon) was built, that uses a plutonium-based device to cause a mixture of tritium and deuterium to undergo nuclear fusion. Such bombs are jacketed in a non-fissile (unenriched) uranium case, and they derive more than half their power from the fission of this material by fast neutrons from the nuclear fusion process.


Uranium was also used in photographic chemicals (especially uranium nitrate as a toner), in lamp filaments for stage lighting bulbs, to improve the appearance of dentures, and in the leather and wood industries for stains and dyes. Uranium salts are mordants of silk or wool. Uranyl acetate and uranyl formate are used as electron-dense "stains" in transmission electron microscopy, to increase the contrast of biological specimens in ultrathin sections and in negative staining of viruses, isolated cell organelles and macromolecules.


In 1972, the French physicist Francis Perrin discovered fifteen ancient and no longer active natural nuclear fission reactors in three separate ore deposits at the Oklo mine in Gabon, West Africa, collectively known as the Oklo Fossil Reactors. The ore deposit is 1.7 billion years old; then, uranium-235 constituted about 3% of the total uranium on Earth. This is high enough to permit a sustained nuclear fission chain reaction to occur, provided other supporting conditions exist. The capacity of the surrounding sediment to contain the nuclear waste products has been cited by the U.S. federal government as supporting evidence for the feasibility to store spent nuclear fuel at the Yucca Mountain nuclear waste repository.


Uranium's average concentration in the Earth's crust is (depending on the reference) 2 to 4 parts per million, or about 40 times as abundant as silver. The Earth's crust from the surface to 25 km (15 mi) down is calculated to contain 1017 kg (2×1017 lb) of uranium while the oceans may contain 1013 kg (2×1013 lb). The concentration of uranium in soil ranges from 0.7 to 11 parts per million (up to 15 parts per million in farmland soil due to use of phosphate fertilizers), and its concentration in sea water is 3 parts per billion.


Uranium-238 is the most stable isotope of uranium, with a half-life of about 4.468×109 years, roughly the age of the Earth. Uranium-235 has a half-life of about 7.13×108 years, and uranium-234 has a half-life of about 2.48×105 years. For natural uranium, about 49% of its alpha rays are emitted by each of 238U atom, and also 49% by 234U (since the latter is formed from the former) and about 2.0% of them by the 235U. When the Earth was young, probably about one-fifth of its uranium was uranium-235, but the percentage of 234U was probably much lower than this.


Most ingested uranium is excreted during digestion. Only 0.5% is absorbed when insoluble forms of uranium, such as its oxide, are ingested, whereas absorption of the more soluble uranyl ion can be up to 5%. However, soluble uranium compounds tend to quickly pass through the body, whereas insoluble uranium compounds, especially when inhaled by way of dust into the lungs, pose a more serious exposure hazard. After entering the bloodstream, the absorbed uranium tends to bioaccumulate and stay for many years in bone tissue because of uranium's affinity for phosphates. Uranium is not absorbed through the skin, and alpha particles released by uranium cannot penetrate the skin.


Appointments to the Order of the British Empire were at first made on the nomination of the self-governing Dominions of the Empire, the Viceroy of India, and the colonial governors, as well as on nominations from within the United Kingdom. As the Empire evolved into the Commonwealth, nominations continued to come from the Commonwealth realms, in which the monarch remained head of state. These overseas nominations have been discontinued in realms that have established their own Orders—such as the Order of Australia, the Order of Canada, and the New Zealand Order of Merit—but members of the Order are still appointed in the British Overseas Territories.


Any individual made a member of the Order for gallantry could wear an emblem of two crossed silver oak leaves on the same riband, ribbon or bow as the badge. It could not be awarded posthumously and was effectively replaced in 1974 with the Queen's Gallantry Medal. If recipients of the Order of the British Empire for Gallantry received promotion within the Order, whether for gallantry or otherwise, they continued to wear also the insignia of the lower grade with the oak leaves. However, they only used the post-nominal letters of the higher grade.


Honorary knighthoods are appointed to citizens of nations where Queen Elizabeth II is not Head of State, and may permit use of post-nominal letters but not the title of Sir or Dame. Occasionally honorary appointees are, incorrectly, referred to as Sir or Dame - Bill Gates or Bob Geldof, for example. Honorary appointees who later become a citizen of a Commonwealth realm can convert their appointment from honorary to substantive, then enjoy all privileges of membership of the order including use of the title of Sir and Dame for the senior two ranks of the Order. An example is Irish broadcaster Terry Wogan, who was appointed an honorary Knight Commander of the Order in 2005 and on successful application for dual British and Irish citizenship was made a substantive member and subsequently styled as "Sir Terry Wogan KBE".


The Order has six officials: the Prelate; the Dean; the Secretary; the Registrar; the King of Arms; and the Usher. The Bishop of London, a senior bishop in the Church of England, serves as the Order's Prelate. The Dean of St Paul's is ex officio the Dean of the Order. The Order's King of Arms is not a member of the College of Arms, as are many other heraldic officers. The Usher of the Order is known as the Gentleman Usher of the Purple Rod; he does not – unlike his Order of the Garter equivalent, the Gentleman Usher of the Black Rod – perform any duties related to the House of Lords.


Appointments to the Order of the British Empire were discontinued in those Commonwealth realms that established a national system of honours and awards such as the Order of Australia, the Order of Canada, and the New Zealand Order of Merit. In many of these systems, the different levels of award and honour reflect the Imperial system they replaced. Canada, Australia, and New Zealand all have (in increasing level of precedence) Members of, Officers of, and Companions to (rather than Commanders of) their respective orders, with both Australia and New Zealand having Knights and Dames as their highest classes.


The members of The Beatles were made MBEs in 1965. John Lennon justified the comparative merits of his investiture by comparing military membership in the Order: "Lots of people who complained about us receiving the MBE [status] received theirs for heroism in the war – for killing people… We received ours for entertaining other people. I'd say we deserve ours more." Lennon later returned his MBE insignia on 25 November 1969 as part of his ongoing peace protests. Other criticism centres on the claim that many recipients of the Order are being rewarded with honours for simply doing their jobs; critics claim that the civil service and judiciary receive far more orders and honours than leaders of other professions.


The Most Excellent Order of the British Empire is the "order of chivalry of British constitutional monarchy", rewarding contributions to the arts and sciences, work with charitable and welfare organisations and public service outside the Civil Service. It was established on 4 June 1917 by King George V, and comprises five classes, in civil and military divisions, the most senior two of which make the recipient either a knight if male, or dame if female. There is also the related British Empire Medal, whose recipients are affiliated with, but not members of, the order.


At the foundation of the Order, the "Medal of the Order of the British Empire" was instituted, to serve as a lower award granting recipients affiliation but not membership. In 1922, this was renamed the "British Empire Medal". It stopped being awarded by the United Kingdom as part of the 1993 reforms to the honours system, but was again awarded beginning in 2012, starting with 293 BEMs awarded for the Queen's Diamond Jubilee. In addition, the BEM is awarded by the Cook Islands and by some other Commonwealth nations. In 2004, a report entitled "A Matter of Honour: Reforming Our Honours System" by a Commons committee recommended to phase out the Order of the British Empire, as its title was "now considered to be unacceptable, being thought to embody values that are no longer shared by many of the country’s population".


From 1940, the Sovereign could appoint a person as a Commander, Officer or Member of the Order of the British Empire for gallantry for acts of bravery (not in the face of the enemy) below the level required for the George Medal. The grade was determined by the same criteria as usual, and not by the level of gallantry (and with more junior people instead receiving the British Empire Medal). Oddly, this meant that it was awarded for lesser acts of gallantry than the George Medal, but, as an Order, was worn before it and listed before it in post-nominal initials. From 14 January 1958, these awards were designated the Order of the British Empire for Gallantry.


Knights Grand Cross and Knights Commander prefix Sir, and Dames Grand Cross and Dames Commander prefix Dame, to their forenames.[b] Wives of Knights may prefix Lady to their surnames, but no equivalent privilege exists for husbands of Knights or spouses of Dames. Such forms are not used by peers and princes, except when the names of the former are written out in their fullest forms. Clergy of the Church of England or the Church of Scotland do not use the title Sir or Dame as they do not receive the accolade (i.e., they are not dubbed "knight" with a sword), although they do append the post-nominal letters.


India, while remaining an active member of the Commonwealth, chose as a republic to institute its own set of honours awarded by the President of India who holds a republican position some consider similar to that of the monarch in Britain. These are commonly referred to as the Padma Awards and consist of Padma Vibhushan, Padma Bhushan and Padma Shri in descending order. These do not carry any decoration or insignia that can be worn on the person and may not be used as titles along with individuals' names.


The Order is limited to 300 Knights and Dames Grand Cross, 845 Knights and Dames Commander, and 8,960 Commanders. There are no limits applied to the total number of members of the fourth and fifth classes, but no more than 858 Officers and 1,464 Members may be appointed per year. Foreign recipients, as honorary members, do not contribute to the numbers restricted to the Order as full members do. Although the Order of the British Empire has by far the highest number of members of the British Orders of Chivalry, with over 100,000 living members worldwide, there are fewer appointments to knighthoods than in other orders.


Members of all classes of the Order are assigned positions in the order of precedence. Wives of male members of all classes also feature on the order of precedence, as do sons, daughters and daughters-in-law of Knights Grand Cross and Knights Commander; relatives of Ladies of the Order, however, are not assigned any special precedence. As a general rule, individuals can derive precedence from their fathers or husbands, but not from their mothers or wives (see order of precedence in England and Wales for the exact positions).


Circadian rhythms allow organisms to anticipate and prepare for precise and regular environmental changes. They thus enable organisms to best capitalize on environmental resources (e.g. light and food) compared to those that cannot predict such availability. It has therefore been suggested that circadian rhythms put organisms at a selective advantage in evolutionary terms. However, rhythmicity appears to be as important in regulating and coordinating internal metabolic processes, as in coordinating with the environment. This is suggested by the maintenance (heritability) of circadian rhythms in fruit flies after several hundred generations in constant laboratory conditions, as well as in creatures in constant darkness in the wild, and by the experimental elimination of behavioral, but not physiological, circadian rhythms in quail.


Norwegian researchers at the University of Tromsø have shown that some Arctic animals (ptarmigan, reindeer) show circadian rhythms only in the parts of the year that have daily sunrises and sunsets. In one study of reindeer, animals at 70 degrees North showed circadian rhythms in the autumn, winter and spring, but not in the summer. Reindeer on Svalbard at 78 degrees North showed such rhythms only in autumn and spring. The researchers suspect that other Arctic animals as well may not show circadian rhythms in the constant light of summer and the constant dark of winter.


The central oscillator generates a self-sustaining rhythm and is driven by two interacting feedback loops that are active at different times of day. The morning loop consists of CCA1 (Circadian and Clock-Associated 1) and LHY (Late Elongated Hypocotyl), which encode closely related MYB transcription factors that regulate circadian rhythms in Arabidopsis, as well as PRR 7 and 9 (Pseudo-Response Regulators.) The evening loop consists of GI (Gigantea) and ELF4, both involved in regulation of flowering time genes. When CCA1 and LHY are overexpressed (under constant light or dark conditions), plants become arrhythmic, and mRNA signals reduce, contributing to a negative feedback loop. Gene expression of CCA1 and LHY oscillates and peaks in the early morning, whereas TOC1 gene expression oscillates and peaks in the early evening. While it was previously hypothesised that these three genes model a negative feedback loop in which over-expressed CCA1 and LHY repress TOC1 and over-expressed TOC1 is a positive regulator of CCA1 and LHY, it was shown in 2012 by Andrew Millar and others that TOC1 in fact serves as a repressor not only of CCA1, LHY, and PRR7 and 9 in the morning loop but also of GI and ELF4 in the evening loop. This finding and further computational modeling of TOC1 gene functions and interactions suggest a reframing of the plant circadian clock as a triple negative-component repressilator model rather than the positive/negative-element feedback loop characterizing the clock in mammals.


A defect in the human homologue of the Drosophila "period" gene was identified as a cause of the sleep disorder FASPS (Familial advanced sleep phase syndrome), underscoring the conserved nature of the molecular circadian clock through evolution. Many more genetic components of the biological clock are now known. Their interactions result in an interlocked feedback loop of gene products resulting in periodic fluctuations that the cells of the body interpret as a specific time of the day.[citation needed]


Due to the work nature of airline pilots, who often cross several timezones and regions of sunlight and darkness in one day, and spend many hours awake both day and night, they are often unable to maintain sleep patterns that correspond to the natural human circadian rhythm; this situation can easily lead to fatigue. The NTSB cites this as contributing to many accidents[unreliable medical source?]  and has conducted several research studies in order to find methods of combating fatigue in pilots.


The earliest recorded account of a circadian process dates from the 4th century B.C.E., when Androsthenes, a ship captain serving under Alexander the Great, described diurnal leaf movements of the tamarind tree. The observation of a circadian or diurnal process in humans is mentioned in Chinese medical texts dated to around the 13th century, including the Noon and Midnight Manual and the Mnemonic Rhyme to Aid in the Selection of Acu-points According to the Diurnal Cycle, the Day of the Month and the Season of the Year.


Plant circadian rhythms tell the plant what season it is and when to flower for the best chance of attracting pollinators. Behaviors showing rhythms include leaf movement, growth, germination, stomatal/gas exchange, enzyme activity, photosynthetic activity, and fragrance emission, among others. Circadian rhythms occur as a plant entrains to synchronize with the light cycle of its surrounding environment. These rhythms are endogenously generated and self-sustaining and are relatively constant over a range of ambient temperatures. Important features include two interacting transcription-translation feedback loops: proteins containing PAS domains, which facilitate protein-protein interactions; and several photoreceptors that fine-tune the clock to different light conditions. Anticipation of changes in the environment allows appropriate changes in a plant's physiological state, conferring an adaptive advantage. A better understanding of plant circadian rhythms has applications in agriculture, such as helping farmers stagger crop harvests to extend crop availability and securing against massive losses due to weather.


The simplest known circadian clock is that of the prokaryotic cyanobacteria. Recent research has demonstrated that the circadian clock of Synechococcus elongatus can be reconstituted in vitro with just the three proteins (KaiA, KaiB, KaiC) of their central oscillator. This clock has been shown to sustain a 22-hour rhythm over several days upon the addition of ATP. Previous explanations of the prokaryotic circadian timekeeper were dependent upon a DNA transcription/translation feedback mechanism.[citation needed]


The rhythm is linked to the light–dark cycle. Animals, including humans, kept in total darkness for extended periods eventually function with a free-running rhythm. Their sleep cycle is pushed back or forward each "day", depending on whether their "day", their endogenous period, is shorter or longer than 24 hours. The environmental cues that reset the rhythms each day are called zeitgebers (from the German, "time-givers"). Totally blind subterranean mammals (e.g., blind mole rat Spalax sp.) are able to maintain their endogenous clocks in the apparent absence of external stimuli. Although they lack image-forming eyes, their photoreceptors (which detect light) are still functional; they do surface periodically as well.[page needed]


Melatonin is absent from the system or undetectably low during daytime. Its onset in dim light, dim-light melatonin onset (DLMO), at roughly 21:00 (9 p.m.) can be measured in the blood or the saliva. Its major metabolite can also be measured in morning urine. Both DLMO and the midpoint (in time) of the presence of the hormone in the blood or saliva have been used as circadian markers. However, newer research indicates that the melatonin offset may be the more reliable marker. Benloucif et al. found that melatonin phase markers were more stable and more highly correlated with the timing of sleep than the core temperature minimum. They found that both sleep offset and melatonin offset are more strongly correlated with phase markers than the onset of sleep. In addition, the declining phase of the melatonin levels is more reliable and stable than the termination of melatonin synthesis.


For temperature studies, subjects must remain awake but calm and semi-reclined in near darkness while their rectal temperatures are taken continuously. Though variation is great among normal chronotypes, the average human adult's temperature reaches its minimum at about 05:00 (5 a.m.), about two hours before habitual wake time. Baehr et al. found that, in young adults, the daily body temperature minimum occurred at about 04:00 (4 a.m.) for morning types but at about 06:00 (6 a.m.) for evening types. This minimum occurred at approximately the middle of the eight hour sleep period for morning types, but closer to waking in evening types.


In 1896, Patrick and Gilbert observed that during a prolonged period of sleep deprivation, sleepiness increases and decreases with a period of approximately 24 hours. In 1918, J.S. Szymanski showed that animals are capable of maintaining 24-hour activity patterns in the absence of external cues such as light and changes in temperature. In the early 20th century, circadian rhythms were noticed in the rhythmic feeding times of bees. Extensive experiments were done by Auguste Forel, Ingeborg Beling, and Oskar Wahl to see whether this rhythm was due to an endogenous clock.[citation needed] Ron Konopka and Seymour Benzer isolated the first clock mutant in Drosophila in the early 1970s and mapped the "period" gene, the first discovered genetic determinant of behavioral rhythmicity. Joseph Takahashi discovered the first mammalian circadian clock mutation (clockΔ19) using mice in 1994. However, recent studies show that deletion of clock does not lead to a behavioral phenotype (the animals still have normal circadian rhythms), which questions its importance in rhythm generation.


It is now known that the molecular circadian clock can function within a single cell; i.e., it is cell-autonomous. This was shown by Gene Block in isolated mollusk BRNs.[clarification needed] At the same time, different cells may communicate with each other resulting in a synchronised output of electrical signaling. These may interface with endocrine glands of the brain to result in periodic release of hormones. The receptors for these hormones may be located far across the body and synchronise the peripheral clocks of various organs. Thus, the information of the time of the day as relayed by the eyes travels to the clock in the brain, and, through that, clocks in the rest of the body may be synchronised. This is how the timing of, for example, sleep/wake, body temperature, thirst, and appetite are coordinately controlled by the biological clock.[citation needed]


Light is the signal by which plants synchronize their internal clocks to their environment and is sensed by a wide variety of photoreceptors. Red and blue light are absorbed through several phytochromes and cryptochromes. One phytochrome, phyA, is the main phytochrome in seedlings grown in the dark but rapidly degrades in light to produce Cry1. Phytochromes B–E are more stable with phyB, the main phytochrome in seedlings grown in the light. The cryptochrome (cry) gene is also a light-sensitive component of the circadian clock and is thought to be involved both as a photoreceptor and as part of the clock's endogenous pacemaker mechanism. Cryptochromes 1–2 (involved in blue–UVA) help to maintain the period length in the clock through a whole range of light conditions.


Studies by Nathaniel Kleitman in 1938 and by Derk-Jan Dijk and Charles Czeisler in the 1990s put human subjects on enforced 28-hour sleep–wake cycles, in constant dim light and with other time cues suppressed, for over a month. Because normal people cannot entrain to a 28-hour day in dim light if at all,[citation needed] this is referred to as a forced desynchrony protocol. Sleep and wake episodes are uncoupled from the endogenous circadian period of about 24.18 hours and researchers are allowed to assess the effects of circadian phase on aspects of sleep and wakefulness including sleep latency and other functions.[page needed]


Shift-work or chronic jet-lag have profound consequences on circadian and metabolic events in the body. Animals that are forced to eat during their resting period show increased body mass and altered expression of clock and metabolic genes.[medical citation needed] In humans, shift-work that favors irregular eating times is associated with altered insulin sensitivity and higher body mass. Shift-work also leads to increased metabolic risks for cardio-metabolic syndrome, hypertension, inflammation.


Studies conducted on both animals and humans show major bidirectional relationships between the circadian system and abusive drugs. It is indicated that these abusive drugs affect the central circadian pacemaker. Individuals suffering from substance abuse display disrupted rhythms. These disrupted rhythms can increase the risk for substance abuse and relapse. It is possible that genetic and/or environmental disturbances to the normal sleep and wake cycle can increase the susceptibility to addiction.


What drove circadian rhythms to evolve has been an enigmatic question. Previous hypotheses emphasized that photosensitive proteins and circadian rhythms may have originated together in the earliest cells, with the purpose of protecting replicating DNA from high levels of damaging ultraviolet radiation during the daytime. As a result, replication was relegated to the dark. However, evidence for this is lacking, since the simplest organisms with a circadian rhythm, the cyanobacteria, do the opposite of this - they divide more in the daytime. Recent studies instead highlight the importance of co-evolution of redox proteins with circadian oscillators in all three kingdoms of life following the Great Oxidation Event approximately 2.3 billion years ago. The current view is that circadian changes in environmental oxygen levels and the production of reactive oxygen species (ROS) in the presence of daylight are likely to have driven a need to evolve circadian rhythms to preempt, and therefore counteract, damaging redox reactions on a daily basis.


Mutations or deletions of clock gene in mice have demonstrated the importance of body clocks to ensure the proper timing of cellular/metabolic events; clock-mutant mice are hyperphagic and obese, and have altered glucose metabolism. In mice, deletion of the Rev-ErbA alpha clock gene facilitates diet-induced obesity and changes the balance between glucose and lipid utilization predisposing to diabetes. However, it is not clear whether there is a strong association between clock gene polymorphisms in humans and the susceptibility to develop the metabolic syndrome.


The primary circadian "clock" in mammals is located in the suprachiasmatic nucleus (or nuclei) (SCN), a pair of distinct groups of cells located in the hypothalamus. Destruction of the SCN results in the complete absence of a regular sleep–wake rhythm. The SCN receives information about illumination through the eyes. The retina of the eye contains "classical" photoreceptors ("rods" and "cones"), which are used for conventional vision. But the retina also contains specialized ganglion cells that are directly photosensitive, and project directly to the SCN, where they help in the entrainment (synchronization) of this master circadian clock.


Early research into circadian rhythms suggested that most people preferred a day closer to 25 hours when isolated from external stimuli like daylight and timekeeping. However, this research was faulty because it failed to shield the participants from artificial light. Although subjects were shielded from time cues (like clocks) and daylight, the researchers were not aware of the phase-delaying effects of indoor electric lights.[dubious – discuss] The subjects were allowed to turn on light when they were awake and to turn it off when they wanted to sleep. Electric light in the evening delayed their circadian phase.[citation needed] A more stringent study conducted in 1999 by Harvard University estimated the natural human rhythm to be closer to 24 hours, 11 minutes: much closer to the solar day but still not perfectly in sync.


More-or-less independent circadian rhythms are found in many organs and cells in the body outside the suprachiasmatic nuclei (SCN), the "master clock". These clocks, called peripheral oscillators, are found in the adrenal gland,[citation needed] oesophagus, lungs, liver, pancreas, spleen, thymus, and skin.[citation needed] Though oscillators in the skin respond to light, a systemic influence has not been proven. There is also some evidence that the olfactory bulb and prostate may experience oscillations when cultured, suggesting that these structures may also be weak oscillators.[citation needed]


Elizabeth's many historic visits and meetings include a state visit to the Republic of Ireland and reciprocal visits to and from the Pope. She has seen major constitutional changes, such as devolution in the United Kingdom, Canadian patriation, and the decolonisation of Africa. She has also reigned through various wars and conflicts involving many of her realms. She is the world's oldest reigning monarch as well as Britain's longest-lived. In 2015, she surpassed the reign of her great-great-grandmother, Queen Victoria, to become the longest-reigning British head of state and the longest-reigning queen regnant in world history.


During the war, plans were drawn up to quell Welsh nationalism by affiliating Elizabeth more closely with Wales. Proposals, such as appointing her Constable of Caernarfon Castle or a patron of Urdd Gobaith Cymru (the Welsh League of Youth), were abandoned for various reasons, which included a fear of associating Elizabeth with conscientious objectors in the Urdd, at a time when Britain was at war. Welsh politicians suggested that she be made Princess of Wales on her 18th birthday. Home Secretary, Herbert Morrison supported the idea, but the King rejected it because he felt such a title belonged solely to the wife of a Prince of Wales and the Prince of Wales had always been the heir apparent. In 1946, she was inducted into the Welsh Gorsedd of Bards at the National Eisteddfod of Wales.


Elizabeth and Philip were married on 20 November 1947 at Westminster Abbey. They received 2500 wedding gifts from around the world. Because Britain had not yet completely recovered from the devastation of the war, Elizabeth required ration coupons to buy the material for her gown, which was designed by Norman Hartnell. In post-war Britain, it was not acceptable for the Duke of Edinburgh's German relations, including his three surviving sisters, to be invited to the wedding. The Duke of Windsor, formerly King Edward VIII, was not invited either.


Amid preparations for the coronation, Princess Margaret informed her sister that she wished to marry Peter Townsend, a divorcé‚ 16 years Margaret's senior, with two sons from his previous marriage. The Queen asked them to wait for a year; in the words of Martin Charteris, "the Queen was naturally sympathetic towards the Princess, but I think she thought—she hoped—given time, the affair would peter out." Senior politicians were against the match and the Church of England did not permit remarriage after divorce. If Margaret had contracted a civil marriage, she would have been expected to renounce her right of succession. Eventually, she decided to abandon her plans with Townsend. In 1960, she married Antony Armstrong-Jones, who was created Earl of Snowdon the following year. They divorced in 1978; she did not remarry.


The Suez crisis and the choice of Eden's successor led in 1957 to the first major personal criticism of the Queen. In a magazine, which he owned and edited, Lord Altrincham accused her of being "out of touch". Altrincham was denounced by public figures and slapped by a member of the public appalled by his comments. Six years later, in 1963, Macmillan resigned and advised the Queen to appoint the Earl of Home as prime minister, advice that she followed. The Queen again came under criticism for appointing the prime minister on the advice of a small number of ministers or a single minister. In 1965, the Conservatives adopted a formal mechanism for electing a leader, thus relieving her of involvement.


A year later, at the height of the 1975 Australian constitutional crisis, the Australian Prime Minister, Gough Whitlam, was dismissed from his post by Governor-General Sir John Kerr, after the Opposition-controlled Senate rejected Whitlam's budget proposals. As Whitlam had a majority in the House of Representatives, Speaker Gordon Scholes appealed to the Queen to reverse Kerr's decision. She declined, stating that she would not interfere in decisions reserved by the Constitution of Australia for the governor-general. The crisis fuelled Australian republicanism.


In 1987, in Canada, Elizabeth publicly supported politically divisive constitutional amendments, prompting criticism from opponents of the proposed changes, including Pierre Trudeau. The same year, the elected Fijian government was deposed in a military coup. Elizabeth, as monarch of Fiji, supported the attempts of the Governor-General, Ratu Sir Penaia Ganilau, to assert executive power and negotiate a settlement. Coup leader Sitiveni Rabuka deposed Ganilau and declared Fiji a republic. By the start of 1991, republican feeling in Britain had risen because of press estimates of the Queen's private wealth—which were contradicted by the Palace—and reports of affairs and strained marriages among her extended family. The involvement of the younger royals in the charity game show It's a Royal Knockout was ridiculed and the Queen was the target of satire.


In 2002, Elizabeth marked her Golden Jubilee. Her sister and mother died in February and March respectively, and the media speculated whether the Jubilee would be a success or a failure. She again undertook an extensive tour of her realms, which began in Jamaica in February, where she called the farewell banquet "memorable" after a power cut plunged the King's House, the official residence of the governor-general, into darkness. As in 1977, there were street parties and commemorative events, and monuments were named to honour the occasion. A million people attended each day of the three-day main Jubilee celebration in London, and the enthusiasm shown by the public for the Queen was greater than many journalists had expected.


The Queen, who opened the 1976 Summer Olympics in Montreal, also opened the 2012 Summer Olympics and Paralympics in London, making her the first head of state to open two Olympic Games in two different countries. For the London Olympics, she played herself in a short film as part of the opening ceremony, alongside Daniel Craig as James Bond. On 4 April 2013, she received an honorary BAFTA for her patronage of the film industry and was called "the most memorable Bond girl yet" at the award ceremony.


Elizabeth's personal fortune has been the subject of speculation for many years. Jock Colville, who was her former private secretary and a director of her bank, Coutts, estimated her wealth in 1971 at £2 million (equivalent to about £25 million today). In 1993, Buckingham Palace called estimates of £100 million "grossly overstated". She inherited an estimated £70 million estate from her mother in 2002. The Sunday Times Rich List 2015 estimated her private wealth at £340 million, making her the 302nd richest person in the UK.


Times of personal significance have included the births and marriages of her children, grandchildren and great grandchildren, her coronation in 1953, and the celebration of milestones such as her Silver, Golden and Diamond Jubilees in 1977, 2002, and 2012, respectively. Moments of sadness for her include the death of her father, aged 56; the assassination of Prince Philip's uncle, Lord Mountbatten; the breakdown of her children's marriages in 1992 (her annus horribilis); the death in 1997 of her son's former wife, Diana, Princess of Wales; and the deaths of her mother and sister in 2002. Elizabeth has occasionally faced republican sentiments and severe press criticism of the royal family, but support for the monarchy and her personal popularity remain high.


Despite the death of Queen Mary on 24 March, the coronation on 2 June 1953 went ahead as planned, as Mary had asked before she died. The ceremony in Westminster Abbey, with the exception of the anointing and communion, was televised for the first time.[d] Elizabeth's coronation gown was embroidered on her instructions with the floral emblems of Commonwealth countries: English Tudor rose; Scots thistle; Welsh leek; Irish shamrock; Australian wattle; Canadian maple leaf; New Zealand silver fern; South African protea; lotus flowers for India and Ceylon; and Pakistan's wheat, cotton, and jute.


In 1957, she made a state visit to the United States, where she addressed the United Nations General Assembly on behalf of the Commonwealth. On the same tour, she opened the 23rd Canadian Parliament, becoming the first monarch of Canada to open a parliamentary session. Two years later, solely in her capacity as Queen of Canada, she revisited the United States and toured Canada. In 1961, she toured Cyprus, India, Pakistan, Nepal, and Iran. On a visit to Ghana the same year, she dismissed fears for her safety, even though her host, President Kwame Nkrumah, who had replaced her as head of state, was a target for assassins. Harold Macmillan wrote, "The Queen has been absolutely determined all through ... She is impatient of the attitude towards her to treat her as ... a film star ... She has indeed 'the heart and stomach of a man' ... She loves her duty and means to be a Queen." Before her tour through parts of Quebec in 1964, the press reported that extremists within the Quebec separatist movement were plotting Elizabeth's assassination. No attempt was made, but a riot did break out while she was in Montreal; the Queen's "calmness and courage in the face of the violence" was noted.


In 1977, Elizabeth marked the Silver Jubilee of her accession. Parties and events took place throughout the Commonwealth, many coinciding with her associated national and Commonwealth tours. The celebrations re-affirmed the Queen's popularity, despite virtually coincident negative press coverage of Princess Margaret's separation from her husband. In 1978, the Queen endured a state visit to the United Kingdom by Romania's communist dictator, Nicolae Ceaușescu, and his wife, Elena, though privately she thought they had "blood on their hands". The following year brought two blows: one was the unmasking of Anthony Blunt, former Surveyor of the Queen's Pictures, as a communist spy; the other was the assassination of her relative and in-law Lord Mountbatten by the Provisional Irish Republican Army.


In the 1950s, as a young woman at the start of her reign, Elizabeth was depicted as a glamorous "fairytale Queen". After the trauma of the Second World War, it was a time of hope, a period of progress and achievement heralding a "new Elizabethan age". Lord Altrincham's accusation in 1957 that her speeches sounded like those of a "priggish schoolgirl" was an extremely rare criticism. In the late 1960s, attempts to portray a more modern image of the monarchy were made in the television documentary Royal Family and by televising Prince Charles's investiture as Prince of Wales. In public, she took to wearing mostly solid-colour overcoats and decorative hats, which allow her to be seen easily in a crowd.


The Royal Collection, which includes thousands of historic works of art and the Crown Jewels, is not owned by the Queen personally but is held in trust, as are her official residences, such as Buckingham Palace and Windsor Castle, and the Duchy of Lancaster, a property portfolio valued in 2014 at £442 million. Sandringham House and Balmoral Castle are privately owned by the Queen. The British Crown Estate – with holdings of £9.4 billion in 2014 – is held in trust by the sovereign and cannot be sold or owned by Elizabeth in a private capacity.


Elizabeth's only sibling, Princess Margaret, was born in 1930. The two princesses were educated at home under the supervision of their mother and their governess, Marion Crawford, who was casually known as "Crawfie". Lessons concentrated on history, language, literature and music. Crawford published a biography of Elizabeth and Margaret's childhood years entitled The Little Princesses in 1950, much to the dismay of the royal family. The book describes Elizabeth's love of horses and dogs, her orderliness, and her attitude of responsibility. Others echoed such observations: Winston Churchill described Elizabeth when she was two as "a character. She has an air of authority and reflectiveness astonishing in an infant." Her cousin Margaret Rhodes described her as "a jolly little girl, but fundamentally sensible and well-behaved".


In 1943, at the age of 16, Elizabeth undertook her first solo public appearance on a visit to the Grenadier Guards, of which she had been appointed colonel the previous year. As she approached her 18th birthday, parliament changed the law so that she could act as one of five Counsellors of State in the event of her father's incapacity or absence abroad, such as his visit to Italy in July 1944. In February 1945, she joined the Women's Auxiliary Territorial Service as an honorary second subaltern with the service number of 230873. She trained as a driver and mechanic and was promoted to honorary junior commander five months later.


The engagement was not without controversy: Philip had no financial standing, was foreign-born (though a British subject who had served in the Royal Navy throughout the Second World War), and had sisters who had married German noblemen with Nazi links. Marion Crawford wrote, "Some of the King's advisors did not think him good enough for her. He was a prince without a home or kingdom. Some of the papers played long and loud tunes on the string of Philip's foreign origin." Elizabeth's mother was reported, in later biographies, to have opposed the union initially, even dubbing Philip "The Hun". In later life, however, she told biographer Tim Heald that Philip was "an English gentleman".


During 1951, George VI's health declined and Elizabeth frequently stood in for him at public events. When she toured Canada and visited President Harry S. Truman in Washington, D.C., in October 1951, her private secretary, Martin Charteris, carried a draft accession declaration in case the King died while she was on tour. In early 1952, Elizabeth and Philip set out for a tour of Australia and New Zealand by way of Kenya. On 6 February 1952, they had just returned to their Kenyan home, Sagana Lodge, after a night spent at Treetops Hotel, when word arrived of the death of the King and consequently Elizabeth's immediate accession to the throne. Philip broke the news to the new Queen. Martin Charteris asked her to choose a regnal name; she chose to remain Elizabeth, "of course". She was proclaimed queen throughout her realms and the royal party hastily returned to the United Kingdom. She and the Duke of Edinburgh moved into Buckingham Palace.


In 1956, the British and French prime ministers, Sir Anthony Eden and Guy Mollet, discussed the possibility of France joining the Commonwealth. The proposal was never accepted and the following year France signed the Treaty of Rome, which established the European Economic Community, the precursor to the European Union. In November 1956, Britain and France invaded Egypt in an ultimately unsuccessful attempt to capture the Suez Canal. Lord Mountbatten claimed the Queen was opposed to the invasion, though Eden denied it. Eden resigned two months later.


The 1960s and 1970s saw an acceleration in the decolonisation of Africa and the Caribbean. Over 20 countries gained independence from Britain as part of a planned transition to self-government. In 1965, however, the Rhodesian Prime Minister, Ian Smith, in opposition to moves toward majority rule, declared unilateral independence from Britain while still expressing "loyalty and devotion" to Elizabeth. Although the Queen dismissed him in a formal declaration, and the international community applied sanctions against Rhodesia, his regime survived for over a decade. As Britain's ties to its former empire weakened, the British government sought entry to the European Community, a goal it achieved in 1973.


During the 1981 Trooping the Colour ceremony and only six weeks before the wedding of Charles, Prince of Wales, and Lady Diana Spencer, six shots were fired at the Queen from close range as she rode down The Mall on her horse, Burmese. Police later discovered that the shots were blanks. The 17-year-old assailant, Marcus Sarjeant, was sentenced to five years in prison and released after three. The Queen's composure and skill in controlling her mount were widely praised. From April to September 1982, the Queen remained anxious but proud of her son, Prince Andrew, who was serving with British forces during the Falklands War. On 9 July, the Queen awoke in her bedroom at Buckingham Palace to find an intruder, Michael Fagan, in the room with her. Remaining calm and through two calls to the Palace police switchboard, she spoke to Fagan while he sat at the foot of her bed until assistance arrived seven minutes later. Though she hosted US President Ronald Reagan at Windsor Castle in 1982 and visited his Californian ranch in 1983, she was angered when his administration ordered the invasion of Grenada, one of her Caribbean realms, without informing her.


In the years to follow, public revelations on the state of Charles and Diana's marriage continued. Even though support for republicanism in Britain seemed higher than at any time in living memory, republicanism was still a minority viewpoint, and the Queen herself had high approval ratings. Criticism was focused on the institution of the monarchy itself and the Queen's wider family rather than her own behaviour and actions. In consultation with her husband and the Prime Minister, John Major, as well as the Archbishop of Canterbury, George Carey, and her private secretary, Robert Fellowes, she wrote to Charles and Diana at the end of December 1995, saying that a divorce was desirable.


The Queen addressed the United Nations for a second time in 2010, again in her capacity as Queen of all Commonwealth realms and Head of the Commonwealth. The UN Secretary General, Ban Ki-moon, introduced her as "an anchor for our age". During her visit to New York, which followed a tour of Canada, she officially opened a memorial garden for the British victims of the September 11 attacks. The Queen's visit to Australia in October 2011 – her sixteenth visit since 1954 – was called her "farewell tour" in the press because of her age.


From 21 April 1944 until her accession, Elizabeth's arms consisted of a lozenge bearing the royal coat of arms of the United Kingdom differenced with a label of three points argent, the centre point bearing a Tudor rose and the first and third a cross of St George. Upon her accession, she inherited the various arms her father held as sovereign. The Queen also possesses royal standards and personal flags for use in the United Kingdom, Canada, Australia, New Zealand, Jamaica, Barbados, and elsewhere.


Elizabeth was born in London to the Duke and Duchess of York, later King George VI and Queen Elizabeth, and was the elder of their two daughters. She was educated privately at home. Her father acceded to the throne on the abdication of his brother Edward VIII in 1936, from which time she was the heir presumptive. She began to undertake public duties during World War II, serving in the Auxiliary Territorial Service. In 1947, she married Philip, Duke of Edinburgh, with whom she has four children: Charles, Anne, Andrew, and Edward.


During her grandfather's reign, Elizabeth was third in the line of succession to the throne, behind her uncle Edward, Prince of Wales, and her father, the Duke of York. Although her birth generated public interest, she was not expected to become queen, as the Prince of Wales was still young, and many assumed that he would marry and have children of his own. When her grandfather died in 1936 and her uncle succeeded as Edward VIII, she became second-in-line to the throne, after her father. Later that year Edward abdicated, after his proposed marriage to divorced socialite Wallis Simpson provoked a constitutional crisis. Consequently, Elizabeth's father became king, and she became heir presumptive. If her parents had had a later son, she would have lost her position as first-in-line, as her brother would have been heir apparent and above her in the line of succession.


With Elizabeth's accession, it seemed probable that the royal house would bear her husband's name, becoming the House of Mountbatten, in line with the custom of a wife taking her husband's surname on marriage. The British Prime Minister, Winston Churchill, and Elizabeth's grandmother, Queen Mary, favoured the retention of the House of Windsor, and so on 9 April 1952 Elizabeth issued a declaration that Windsor would continue to be the name of the royal house. The Duke complained, "I am the only man in the country not allowed to give his name to his own children." In 1960, after the death of Queen Mary in 1953 and the resignation of Churchill in 1955, the surname Mountbatten-Windsor was adopted for Philip and Elizabeth's male-line descendants who do not carry royal titles.


The absence of a formal mechanism within the Conservative Party for choosing a leader meant that, following Eden's resignation, it fell to the Queen to decide whom to commission to form a government. Eden recommended that she consult Lord Salisbury, the Lord President of the Council. Lord Salisbury and Lord Kilmuir, the Lord Chancellor, consulted the British Cabinet, Winston Churchill, and the Chairman of the backbench 1922 Committee, resulting in the Queen appointing their recommended candidate: Harold Macmillan.