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The island of Saint Helena has a total area of 122 km2 (47 sq mi), and is composed largely of rugged terrain of volcanic origin (the last volcanic eruptions occurred about 7 million years ago). Coastal areas are covered in volcanic rock and warmer and drier than the centre. The highest point of the island is Diana's Peak at 818 m (2,684 ft). In 1996 it became the island's first national park. Much of the island is covered by New Zealand flax, a legacy of former industry, but there are some original trees augmented by plantations, including those of the Millennium Forest project which was established in 2002 to replant part of the lost Great Wood and is now managed by the Saint Helena National Trust. When the island was discovered, it was covered with unique indigenous vegetation, including a remarkable cabbage tree species. The island's hinterland must have been a dense tropical forest but the coastal areas were probably also quite green. The modern landscape is very different, with widespread bare rock in the lower areas, although inland it is green, mainly due to introduced vegetation. There are no native land mammals, but cattle, cats, dogs, donkeys, goats, mice, rabbits, rats and sheep have been introduced, and native species have been adversely affected as a result. The dramatic change in landscape must be attributed to these introductions. As a result, the string tree (Acalypha rubrinervis) and the St Helena olive (Nesiota elliptica) are now extinct, and many of the other endemic plants are threatened with extinction.
There are several rocks and islets off the coast, including: Castle Rock, Speery Island, the Needle, Lower Black Rock, Upper Black Rock (South), Bird Island (Southwest), Black Rock, Thompson's Valley Island, Peaked Island, Egg Island, Lady's Chair, Lighter Rock (West), Long Ledge (Northwest), Shore Island, George Island, Rough Rock Island, Flat Rock (East), the Buoys, Sandy Bay Island, the Chimney, White Bird Island and Frightus Rock (Southeast), all of which are within one kilometre (0.62 miles) of the shore.
The national bird of Saint Helena is the Saint Helena plover, known locally as the wirebird. It appears on the coat of arms of Saint Helena and on the flag.
The climate of Saint Helena is tropical, marine and mild, tempered by the Benguela Current and trade winds that blow almost continuously. The climate varies noticeably across the island. Temperatures in Jamestown, on the north leeward shore, range between 21–28 °C (70–82 °F) in the summer (January to April) and 17–24 °C (63–75 °F) during the remainder of the year. The temperatures in the central areas are, on average, 5–6 °C (9.0–10.8 °F) lower. Jamestown also has a very low annual rainfall, while 750–1,000 mm (30–39 in) falls per year on the higher ground and the south coast, where it is also noticeably cloudier. There are weather recording stations in the Longwood and Blue Hill districts.
Saint Helena is divided into eight districts, each with a community centre. The districts also serve as statistical subdivisions. The island is a single electoral area and elects twelve representatives to the Legislative Council of fifteen.
Saint Helena was first settled by the English in 1659, and the island has a population of about 4,250 inhabitants, mainly descended from people from Britain – settlers ("planters") and soldiers – and slaves who were brought there from the beginning of settlement – initially from Africa (the Cape Verde Islands, Gold Coast and west coast of Africa are mentioned in early records), then India and Madagascar. Eventually the planters felt there were too many slaves and no more were imported after 1792.
In 1840, St Helena became a provisioning station for the British West Africa Squadron, preventing slavery to Brazil (mainly), and many thousands of slaves were freed on the island. These were all African, and about 500 stayed while the rest were sent on to the West Indies and Cape Town, and eventually to Sierra Leone.
Imported Chinese labourers arrived in 1810, reaching a peak of 618 in 1818, after which numbers were reduced. Only a few older men remained after the British Crown took over the government of the island from the East India Company in 1834. The majority were sent back to China, although records in the Cape suggest that they never got any farther than Cape Town. There were also a very few Indian lascars who worked under the harbour master.
The citizens of Saint Helena hold British Overseas Territories citizenship. On 21 May 2002, full British citizenship was restored by the British Overseas Territories Act 2002. See also British nationality law.
During periods of unemployment, there has been a long pattern of emigration from the island since the post-Napoleonic period. The majority of "Saints" emigrated to the UK, South Africa and in the early years, Australia. The population has steadily declined since the late 1980s and has dropped from 5,157 at the 1998 census to 4,255 in 2008. In the past emigration was characterised by young unaccompanied persons leaving to work on long-term contracts on Ascension and the Falkland Islands, but since "Saints" were re-awarded UK citizenship in 2002, emigration to the UK by a wider range of wage-earners has accelerated due to the prospect of higher wages and better progression prospects.
Most residents belong to the Anglican Communion and are members of the Diocese of St Helena, which has its own bishop and includes Ascension Island. The 150th anniversary of the diocese was celebrated in June 2009.
Other Christian denominations on the island include: Roman Catholic (since 1852), Salvation Army (since 1884), Baptist (since 1845) and, in more recent times, Seventh-day Adventist (since 1949), New Apostolic and Jehovah's Witnesses (of which one in 35 residents is a member, the highest ratio of any country). The Catholics are pastorally served by the Mission sui iuris of Saint Helena, Ascension and Tristan da Cunha, whose office of ecclesiastical superior is vested in the Apostolic Prefecture of the Falkland Islands.
Executive authority in Saint Helena is vested in Queen Elizabeth II and is exercised on her behalf by the Governor of Saint Helena. The Governor is appointed by the Queen on the advice of the British government. Defence and Foreign Affairs remain the responsibility of the United Kingdom.
There are fifteen seats in the Legislative Council of Saint Helena, a unicameral legislature, in addition to a Speaker and a Deputy Speaker. Twelve of the fifteen members are elected in elections held every four years. The three ex officio members are the Chief Secretary, Financial Secretary and Attorney General. The Executive Council is presided over by the Governor, and consists of three ex officio officers and five elected members of the Legislative Council appointed by the Governor. There is no elected Chief Minister, and the Governor acts as the head of government. In January 2013 it was proposed that the Executive Council would be led by a "Chief Councillor" who would be elected by the members of the Legislative Council and would nominate the other members of the Executive Council. These proposals were put to a referendum on 23 March 2013 where they were defeated by 158 votes to 42 on a 10% turnout.
One commentator has observed that, notwithstanding the high unemployment resulting from the loss of full passports during 1981–2002, the level of loyalty to the British monarchy by the St Helena population is probably not exceeded in any other part of the world. King George VI is the only reigning monarch to have visited the island. This was in 1947 when the King, accompanied by Queen Elizabeth (later the Queen Mother), Princess Elizabeth (later Queen Elizabeth II) and Princess Margaret were travelling to South Africa. Prince Philip arrived at St Helena in 1957 and then his son Prince Andrew visited as a member of the armed forces in 1984 and his sister the Princess Royal arrived in 2002.
In 2012, the government of St. Helena funded the creation of the St. Helena Human Rights Action Plan 2012-2015. Work is being done under this action plan, including publishing awareness-raising articles in local newspapers, providing support for members of the public with human rights queries, and extending several UN Conventions on human rights to St. Helena.
In recent years[when?], there have been reports of child abuse in St Helena. Britain’s Foreign and Commonwealth Office (FCO) has been accused of lying to the United Nations about child abuse in St Helena to cover up allegations, including cases of a police officer having raped a four-year-old girl and of a police officer having mutilated a two-year-old.
St Helena has long been known for its high proportion of endemic birds and vascular plants. The highland areas contain most of the 400 endemic species recognised to date. Much of the island has been identified by BirdLife International as being important for bird conservation, especially the endemic Saint Helena plover or wirebird, and for seabirds breeding on the offshore islets and stacks, in the north-east and the south-west Important Bird Areas. On the basis of these endemics and an exceptional range of habitats, Saint Helena is on the United Kingdom's tentative list for future UNESCO World Heritage Sites.
St Helena's biodiversity, however, also includes marine vertebrates, invertebrates (freshwater, terrestrial and marine), fungi (including lichen-forming species), non-vascular plants, seaweeds and other biological groups. To date, very little is known about these, although more than 200 lichen-forming fungi have been recorded, including 9 endemics, suggesting that many significant discoveries remain to be made.
The island had a monocrop economy until 1966, based on the cultivation and processing of New Zealand flax for rope and string. St Helena's economy is now weak, and is almost entirely sustained by aid from the British government. The public sector dominates the economy, accounting for about 50% of gross domestic product. Inflation was running at 4% in 2005. There have been increases in the cost of fuel, power and all imported goods.
The tourist industry is heavily based on the promotion of Napoleon's imprisonment. A golf course also exists and the possibility for sportfishing tourism is great. Three hotels operate on the island but the arrival of tourists is directly linked to the arrival and departure schedule of the RMS St Helena. Some 3,200 short-term visitors arrived on the island in 2013.
Saint Helena produces what is said to be the most expensive coffee in the world. It also produces and exports Tungi Spirit, made from the fruit of the prickly or cactus pears, Opuntia ficus-indica ("Tungi" is the local St Helenian name for the plant). Ascension Island, Tristan da Cunha and Saint Helena all issue their own postage stamps which provide a significant income.
Quoted at constant 2002 prices, GDP fell from £12 million in 1999-2000 to £11 million in 2005-06. Imports are mainly from the UK and South Africa and amounted to £6.4 million in 2004-05 (quoted on an FOB basis). Exports are much smaller, amounting to £0.2 million in 2004-05. Exports are mainly fish and coffee; Philatelic sales were £0.06 million in 2004-05. The limited number of visiting tourists spent about £0.4 million in 2004-05, representing a contribution to GDP of 3%.
Public expenditure rose from £10 million in 2001-02 to £12 million in 2005-06 to £28m in 2012-13. The contribution of UK budgetary aid to total SHG government expenditure rose from £4.6 million in to £6.4 million to £12.1 million over the same period. Wages and salaries represent about 38% of recurrent expenditure.
Unemployment levels are low (31 individuals in 2013, compared to 50 in 2004 and 342 in 1998). Employment is dominated by the public sector, the number of government positions has fallen from 1,142 in 2006 to just over 800 in 2013. St Helena’s private sector employs approximately 45% of the employed labour force and is largely dominated by small and micro businesses with 218 private businesses employing 886 in 2004.
Household survey results suggest the percentage of households spending less than £20 per week on a per capita basis fell from 27% to 8% between 2000 and 2004, implying a decline in income poverty. Nevertheless, 22% of the population claimed social security benefit in 2006/7, most of them aged over 60, a sector that represents 20% of the population.
In 1821, Saul Solomon issued a 70,560 copper tokens worth a halfpenny each Payable at St Helena by Solomon, Dickson and Taylor – presumably London partners – that circulated alongside the East India Company's local coinage until the Crown took over the island in 1836. The coin remains readily available to collectors.
Today Saint Helena has its own currency, the Saint Helena pound, which is at parity with the pound sterling. The government of Saint Helena produces its own coinage and banknotes. The Bank of Saint Helena was established on Saint Helena and Ascension Island in 2004. It has branches in Jamestown on Saint Helena, and Georgetown, Ascension Island and it took over the business of the St. Helena government savings bank and Ascension Island Savings Bank.
Saint Helena is one of the most remote islands in the world, has one commercial airport under construction, and travel to the island is by ship only. A large military airfield is located on Ascension Island, with two Friday flights to RAF Brize Norton, England (as from September 2010). These RAF flights offer a limited number of seats to civilians.
The ship RMS Saint Helena runs between St Helena and Cape Town on a 5-day voyage, also visiting Ascension Island and Walvis Bay, and occasionally voyaging north to Tenerife and Portland, UK. It berths in James Bay, St Helena approximately thirty times per year. The RMS Saint Helena was due for decommissioning in 2010. However, its service life has been extended indefinitely until the airport is completed.
After a long period of rumour and consultation, the British government announced plans to construct an airport in Saint Helena in March 2005. The airport was expected to be completed by 2010. However an approved bidder, the Italian firm Impregilo, was not chosen until 2008, and then the project was put on hold in November 2008, allegedly due to new financial pressures brought on by the Financial crisis of 2007–2010. By January 2009, construction had not commenced and no final contracts had been signed. Governor Andrew Gurr departed for London in an attempt to speed up the process and solve the problems.
On 22 July 2010, the British government agreed to help pay for the new airport using taxpayer money. In November 2011 a new deal between the British government and South African civil engineering company Basil Read was signed and the airport was scheduled to open in February 2016, with flights to and from South Africa and the UK. In March 2015 South African airline Comair became the preferred bidder to provide weekly air service between the island and Johannesburg, starting from 2016.
The first aircraft, a South African Beechcraft King Air 200, landed at the new airport on 15 September 2015, prior to conducting a series of flights to calibrate the airport's radio navigation equipment.
The first helicopter landing at the new airfield was conducted by the Wildcat HMA.2 ZZ377 from 825 Squadron 201 Flight, embarked on visiting HMS Lancaster on 23 October 2015.
A minibus offers a basic service to carry people around Saint Helena, with most services designed to take people into Jamestown for a few hours on weekdays to conduct their business. Car hire is available for visitors.
Radio St Helena, which started operations on Christmas Day 1967, provided a local radio service that had a range of about 100 km (62 mi) from the island, and also broadcast internationally on shortwave radio (11092.5 kHz) on one day a year. The station presented news, features and music in collaboration with its sister newspaper, the St Helena Herald. It closed on 25 December 2012 to make way for a new three-channel FM service, also funded by St. Helena Government and run by the South Atlantic Media Services (formerly St. Helena Broadcasting (Guarantee) Corporation).
Saint FM provided a local radio service for the island which was also available on internet radio and relayed in Ascension Island. The station was not government funded. It was launched in January 2005 and closed on 21 December 2012. It broadcast news, features and music in collaboration with its sister newspaper, the St Helena Independent (which continues).
Saint FM Community Radio took over the radio channels vacated by Saint FM and launched on 10 March 2013. The station operates as a limited-by-guarantee company owned by its members and is registered as a fund-raising Association. Membership is open to everyone, and grants access to a live audio stream.
St Helena Online is a not-for-profit internet news service run from the UK by a former print and BBC journalist, working in partnership with Saint FM and the St Helena Independent.
Sure South Atlantic Ltd ("Sure") offers television for the island via 17 analogue terrestrial UHF channels, offering a mix of British, US, and South African programming. The channels are from DSTV and include Mnet, SuperSport and BBC channels. The feed signal, from MultiChoice DStv in South Africa, is received by a satellite dish at Bryant's Beacon from Intelsat 7 in the Ku band.
SURE provide the telecommunications service in the territory through a digital copper-based telephone network including ADSL-broadband service. In August 2011 the first fibre-optic link has been installed on the island, which connects the television receive antennas at Bryant's Beacon to the Cable & Wireless Technical Centre in the Briars.
A satellite ground station with a 7.6-metre (25 ft) satellite dish installed in 1989 at The Briars is the only international connection providing satellite links through Intelsat 707 to Ascension island and the United Kingdom. Since all international telephone and internet communications are relying on this single satellite link both internet and telephone service are subject to sun outages.
Saint Helena has the international calling code +290 which, since 2006, Tristan da Cunha shares. Saint Helena telephone numbers changed from 4 to 5 digits on 1 October 2013 by being prefixed with the digit "2", i.e. 2xxxx, with the range 5xxxx being reserved for mobile numbering, and 8xxx being used for Tristan da Cunha numbers (these still shown as 4 digits).
Saint Helena has a 10/3.6 Mbit/s internet link via Intelsat 707 provided by SURE. Serving a population of more than 4,000, this single satellite link is considered inadequate in terms of bandwidth.
ADSL-broadband service is provided with maximum speeds of up to 1536 KBit/s downstream and 512 KBit/s upstream offered on contract levels from lite £16 per month to gold+ at £190 per month. There are a few public WiFi hotspots in Jamestown, which are also being operated by SURE (formerly Cable & Wireless).
The South Atlantic Express, a 10,000 km (6,214 mi) submarine communications cable connecting Africa to South America, run by the undersea fibre optic provider eFive, will pass St Helena relatively closely. There were no plans to land the cable and install a landing station ashore, which could supply St Helena's population with sufficient bandwidth to fully leverage the benefits of today's Information Society. In January 2012, a group of supporters petitioned the UK government to meet the cost of landing the cable at St Helena. On 6 October 2012, eFive agreed to reroute the cable through St. Helena after a successful lobbying campaign by A Human Right, a San Francisco-based NGA working on initiatives to ensure all people are connected to the Internet. Islanders have sought the assistance of the UK Department for International Development and Foreign and Commonwealth Office in funding the £10m required to bridge the connection from a local junction box on the cable to the island. The UK Government have announced that a review of the island's economy would be required before such funding would be agreed to.
The island has two local newspapers, both of which are available on the Internet. The St Helena Independent has been published since November 2005. The Sentinel newspaper was introduced in 2012.
Education is free and compulsory between the ages of 5 and 16 The island has three primary schools for students of age 4 to 11: Harford, Pilling, and St Paul’s. Prince Andrew School provides secondary education for students aged 11 to 18. At the beginning of the academic year 2009-10, 230 students were enrolled in primary school and 286 in secondary school.
The Education and Employment Directorate also offers programmes for students with special needs, vocational training, adult education, evening classes, and distance learning. The island has a public library (the oldest in the Southern Hemisphere) and a mobile library service which operates weekly rural areas.
The UK national curriculum is adapted for local use. A range of qualifications are offered – from GCSE, A/S and A2, to Level 3 Diplomas and VRQ qualifications:
Sports played on the island include football, cricket, volleyball, tennis, golf, motocross, shooting sports and yachting. Saint Helena has sent teams to a number of Commonwealth Games. Saint Helena is a member of the International Island Games Association. The Saint Helena cricket team made its debut in international cricket in Division Three of the African region of the World Cricket League in 2011.
The Governor's Cup is a yacht race between Cape Town and Saint Helena island, held every two years in December/January; the most recent event was in December 2010. In Jamestown a timed run takes place up Jacob's Ladder every year, with people coming from all over the world to take part.
There are scouting and guiding groups on Saint Helena and Ascension Island. Scouting was established on Saint Helena island in 1912. Lord and Lady Baden-Powell visited the Scouts on Saint Helena on the return from their 1937 tour of Africa. The visit is described in Lord Baden-Powell's book entitled African Adventures.
In phonetics, aspiration is the strong burst of breath that accompanies either the release or, in the case of preaspiration, the closure of some obstruents. In English, aspirated consonants are allophones in complementary distribution with their unaspirated counterparts, but in some other languages, notably most Indian and East Asian languages, the difference is contrastive.
To feel or see the difference between aspirated and unaspirated sounds, one can put a hand or a lit candle in front of one's mouth, and say pin [pʰɪn] and then spin [spɪn]. One should either feel a puff of air or see a flicker of the candle flame with pin that one does not get with spin. In most dialects of English, the initial consonant is aspirated in pin and unaspirated in spin.
In the International Phonetic Alphabet (IPA), aspirated consonants are written using the symbols for voiceless consonants followed by the aspiration modifier letter ⟨◌ʰ⟩, a superscript form of the symbol for the voiceless glottal fricative ⟨h⟩. For instance, ⟨p⟩ represents the voiceless bilabial stop, and ⟨pʰ⟩ represents the aspirated bilabial stop.
Voiced consonants are seldom actually aspirated. Symbols for voiced consonants followed by ⟨◌ʰ⟩, such as ⟨bʰ⟩, typically represent consonants with breathy voiced release (see below). In the grammatical tradition of Sanskrit, aspirated consonants are called voiceless aspirated, and breathy-voiced consonants are called voiced aspirated.
There are no dedicated IPA symbols for degrees of aspiration and typically only two degrees are marked: unaspirated ⟨k⟩ and aspirated ⟨kʰ⟩. An old symbol for light aspiration was ⟨ʻ⟩, but this is now obsolete. The aspiration modifier letter may be doubled to indicate especially strong or long aspiration. Hence, the two degrees of aspiration in Korean stops are sometimes transcribed ⟨kʰ kʰʰ⟩ or ⟨kʻ⟩ and ⟨kʰ⟩, but they are usually transcribed [k] and [kʰ], with the details of voice-onset time given numerically.
Preaspirated consonants are marked by placing the aspiration modifier letter before the consonant symbol: ⟨ʰp⟩ represents the preaspirated bilabial stop.
Unaspirated or tenuis consonants are occasionally marked with the modifier letter for unaspiration ⟨◌˭⟩, a superscript equal sign: ⟨t˭⟩. Usually, however, unaspirated consonants are left unmarked: ⟨t⟩.
Voiceless consonants are produced with the vocal folds open (spread) and not vibrating, and voiced consonants are produced when the vocal folds are fractionally closed and vibrating (modal voice). Voiceless aspiration occurs when the vocal cords remain open after a consonant is released. An easy way to measure this is by noting the consonant's voice-onset time, as the voicing of a following vowel cannot begin until the vocal cords close.
Phonetically in some languages, such as Navajo, aspiration of stops tends to be realised as voiceless velar airflow; aspiration of affricates is realised as an extended length of the frication.
Aspirated consonants are not always followed by vowels or other voiced sounds. For example, in Eastern Armenian, aspiration is contrastive even word-finally, and aspirated consonants occur in consonant clusters. In Wahgi, consonants are aspirated only in final position.
Armenian and Cantonese have aspiration that lasts about as long as English aspirated stops, in addition to unaspirated stops. Korean has lightly aspirated stops that fall between the Armenian and Cantonese unaspirated and aspirated stops as well as strongly aspirated stops whose aspiration lasts longer than that of Armenian or Cantonese. (See voice-onset time.)
Aspiration varies with place of articulation. The Spanish voiceless stops /p t k/ have voice-onset times (VOTs) of about 5, 10, and 30 milliseconds, whereas English aspirated /p t k/ have VOTs of about 60, 70, and 80 ms. Voice-onset time in Korean has been measured at 20, 25, and 50 ms for /p t k/ and 90, 95, and 125 for /pʰ tʰ kʰ/.
When aspirated consonants are doubled or geminated, the stop is held longer and then has an aspirated release. An aspirated affricate consists of a stop, fricative, and aspirated release. A doubled aspirated affricate has a longer hold in the stop portion and then has a release consisting of the fricative and aspiration.
Icelandic and Faroese have preaspirated [ʰp ʰt ʰk]; some scholars interpret these as consonant clusters as well. In Icelandic, preaspirated stops contrast with double stops and single stops:
Preaspirated stops also occur in most Sami languages; for example, in North Sami, the unvoiced stop and affricate phonemes /p/, /t/, /ts/, /tʃ/, /k/ are pronounced preaspirated ([ʰp], [ʰt] [ʰts], [ʰtʃ], [ʰk]) when they occur in medial or final position.
Although most aspirated obstruents in the world's language are stops and affricates, aspirated fricatives such as [sʰ], [fʰ] or [ɕʰ] have been documented in Korean, in a few Tibeto-Burman languages, in some Oto-Manguean languages, and in the Siouan language Ofo. Some languages, such as Choni Tibetan, have up to four contrastive aspirated fricatives [sʰ] [ɕʰ], [ʂʰ] and [xʰ].
True aspirated voiced consonants, as opposed to murmured (breathy-voice) consonants such as the [bʱ], [dʱ], [ɡʱ] that are common in the languages of India, are extremely rare. They have been documented in Kelabit Taa, and the Kx'a languages. Reported aspirated voiced stops, affricates and clicks are [b͡pʰ, d͡tʰ, d͡tsʰ, d͡tʃʰ, ɡ͡kʰ, ɢ͡qʰ, ᶢʘʰ, ᶢǀʰ, ᶢǁʰ, ᶢǃʰ, ᶢǂʰ].
Aspiration has varying significance in different languages. It is either allophonic or phonemic, and may be analyzed as an underlying consonant cluster.
In some languages, such as English, aspiration is allophonic. Stops are distinguished primarily by voicing, and voiceless stops are sometimes aspirated, while voiced stops are usually unaspirated.
They are unaspirated for almost all speakers when immediately following word-initial s, as in spill, still, skill. After an s elsewhere in a word they are normally unaspirated as well, except sometimes in compound words. When the consonants in a cluster like st are analyzed as belonging to different morphemes (heteromorphemic) the stop is aspirated, but when they are analyzed as belonging to one morpheme the stop is unaspirated.[citation needed] For instance, distend has unaspirated [t] since it is not analyzed as two morphemes, but distaste has an aspirated middle [tʰ] because it is analyzed as dis- + taste and the word taste has an aspirated initial t.
In many languages, such as Armenian, Korean, Thai, Indo-Aryan languages, Dravidian languages, Icelandic, Ancient Greek, and the varieties of Chinese, tenuis and aspirated consonants are phonemic. Unaspirated consonants like [p˭ s˭] and aspirated consonants like [pʰ ʰp sʰ] are separate phonemes, and words are distinguished by whether they have one or the other.
In Danish and most southern varieties of German, the "lenis" consonants transcribed for historical reasons as ⟨b d ɡ⟩ are distinguished from their fortis counterparts ⟨p t k⟩, mainly in their lack of aspiration.
Standard Chinese (Mandarin) has stops and affricates distinguished by aspiration: for instance, /t tʰ/, /t͡s t͡sʰ/. In pinyin, tenuis stops are written with letters that represent voiced consonants in English, and aspirated stops with letters that represent voiceless consonants. Thus d represents /t/, and t represents /tʰ/.
Wu Chinese has a three-way distinction in stops and affricates: /p pʰ b/. In addition to aspirated and unaspirated consonants, there is a series of muddy consonants, like /b/. These are pronounced with slack or breathy voice: that is, they are weakly voiced. Muddy consonants as initial cause a syllable to be pronounced with low pitch or light (陽 yáng) tone.
Many Indo-Aryan languages have aspirated stops. Sanskrit, Hindi, Bengali, Marathi, and Gujarati have a four-way distinction in stops: voiceless, aspirated, voiced, and breathy-voiced or voiced aspirated, such as /p pʰ b bʱ/. Punjabi has lost breathy-voiced consonants, which resulted in a tone system, and therefore has a distinction between voiceless, aspirated, and voiced: /p pʰ b/.
Some of the Dravidian languages, such as Telugu, Tamil, Malayalam, and Kannada, have a distinction between voiced and voiceless, aspirated and unaspirated only in loanwords from Indo-Aryan languages. In native Dravidian words, there is no distinction between these categories and stops are underspecified for voicing and aspiration.
Western Armenian has a two-way distinction between aspirated and voiced: /tʰ d/. Western Armenian aspirated /tʰ/ corresponds to Eastern Armenian aspirated /tʰ/ and voiced /d/, and Western voiced /d/ corresponds to Eastern voiceless /t/.
Some forms of Greek before the Koine Greek period are reconstructed as having aspirated stops. The Classical Attic dialect of Ancient Greek had a three-way distinction in stops like Eastern Armenian: /t tʰ d/. These stops were called ψιλά, δασέα, μέσα "thin, thick, middle" by Koine Greek grammarians.
There were aspirated stops at three places of articulation: labial, coronal, and velar /pʰ tʰ kʰ/. Earlier Greek, represented by Mycenaean Greek, likely had a labialized velar aspirated stop /kʷʰ/, which later became labial, coronal, or velar depending on dialect and phonetic environment.
The other Ancient Greek dialects, Ionic, Doric, Aeolic, and Arcadocypriot, likely had the same three-way distinction at one point, but Doric seems to have had a fricative in place of /tʰ/ in the Classical period, and the Ionic and Aeolic dialects sometimes lost aspiration (psilosis).
Later, during the Koine Greek period, the aspirated and voiceless stops /tʰ d/ of Attic Greek lenited to voiceless and voiced fricatives, yielding /θ ð/ in Medieval and Modern Greek.
The term aspiration sometimes refers to the sound change of debuccalization, in which a consonant is lenited (weakened) to become a glottal stop or fricative [ʔ h ɦ].
So-called voiced aspirated consonants are nearly always pronounced instead with breathy voice, a type of phonation or vibration of the vocal folds. The modifier letter ⟨◌ʰ⟩ after a voiced consonant actually represents a breathy-voiced or murmured dental stop, as with the "voiced aspirated" bilabial stop ⟨bʰ⟩ in the Indo-Aryan languages. This consonant is therefore more accurately transcribed as ⟨b̤⟩, with the diacritic for breathy voice, or with the modifier letter ⟨bʱ⟩, a superscript form of the symbol for the voiced glottal fricative ⟨ɦ⟩.
Some linguists restrict the double-dot subscript ⟨◌̤⟩ to murmured sonorants, such as vowels and nasals, which are murmured throughout their duration, and use the superscript hook-aitch ⟨◌ʱ⟩ for the breathy-voiced release of obstruents.
Hydrogen is a chemical element with chemical symbol H and atomic number 1. With an atomic weight of 7000100794000000000♠1.00794 u, hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass.[note 1] Non-remnant stars are mainly composed of hydrogen in its plasma state. The most common isotope of hydrogen, termed protium (name rarely used, symbol 1H), has one proton and no neutrons.
The universal emergence of atomic hydrogen first occurred during the recombination epoch. At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula H2. Since hydrogen readily forms covalent compounds with most non-metallic elements, most of the hydrogen on Earth exists in molecular forms such as in the form of water or organic compounds. Hydrogen plays a particularly important role in acid–base reactions as many acid-base reactions involve the exchange of protons between soluble molecules. In ionic compounds, hydrogen can take the form of a negative charge (i.e., anion) when it is known as a hydride, or as a positively charged (i.e., cation) species denoted by the symbol H+. The hydrogen cation is written as though composed of a bare proton, but in reality, hydrogen cations in ionic compounds are always more complex species than that would suggest. As the only neutral atom for which the Schrödinger equation can be solved analytically, study of the energetics and bonding of the hydrogen atom has played a key role in the development of quantum mechanics.
Hydrogen gas was first artificially produced in the early 16th century, via the mixing of metals with acids. In 1766–81, Henry Cavendish was the first to recognize that hydrogen gas was a discrete substance, and that it produces water when burned, a property which later gave it its name: in Greek, hydrogen means "water-former".
Industrial production is mainly from the steam reforming of natural gas, and less often from more energy-intensive hydrogen production methods like the electrolysis of water. Most hydrogen is employed near its production site, with the two largest uses being fossil fuel processing (e.g., hydrocracking) and ammonia production, mostly for the fertilizer market. Hydrogen is a concern in metallurgy as it can embrittle many metals, complicating the design of pipelines and storage tanks.
Hydrogen gas (dihydrogen or molecular hydrogen) is highly flammable and will burn in air at a very wide range of concentrations between 4% and 75% by volume. The enthalpy of combustion for hydrogen is −286 kJ/mol:
Hydrogen gas forms explosive mixtures with air if it is 4–74% concentrated and with chlorine if it is 5–95% concentrated. The mixtures may be ignited by spark, heat or sunlight. The hydrogen autoignition temperature, the temperature of spontaneous ignition in air, is 500 °C (932 °F). Pure hydrogen-oxygen flames emit ultraviolet light and with high oxygen mix are nearly invisible to the naked eye, as illustrated by the faint plume of the Space Shuttle Main Engine compared to the highly visible plume of a Space Shuttle Solid Rocket Booster. The detection of a burning hydrogen leak may require a flame detector; such leaks can be very dangerous. Hydrogen flames in other conditions are blue, resembling blue natural gas flames. The destruction of the Hindenburg airship was an infamous example of hydrogen combustion; the cause is debated, but the visible orange flames were the result of a rich mixture of hydrogen to oxygen combined with carbon compounds from the airship skin.
H2 reacts with every oxidizing element. Hydrogen can react spontaneously and violently at room temperature with chlorine and fluorine to form the corresponding hydrogen halides, hydrogen chloride and hydrogen fluoride, which are also potentially dangerous acids.
The energy levels of hydrogen can be calculated fairly accurately using the Bohr model of the atom, which conceptualizes the electron as "orbiting" the proton in analogy to the Earth's orbit of the Sun. However, the electromagnetic force attracts electrons and protons to one another, while planets and celestial objects are attracted to each other by gravity. Because of the discretization of angular momentum postulated in early quantum mechanics by Bohr, the electron in the Bohr model can only occupy certain allowed distances from the proton, and therefore only certain allowed energies.
A more accurate description of the hydrogen atom comes from a purely quantum mechanical treatment that uses the Schrödinger equation, Dirac equation or even the Feynman path integral formulation to calculate the probability density of the electron around the proton. The most complicated treatments allow for the small effects of special relativity and vacuum polarization. In the quantum mechanical treatment, the electron in a ground state hydrogen atom has no angular momentum at all—an illustration of how the "planetary orbit" conception of electron motion differs from reality.
There exist two different spin isomers of hydrogen diatomic molecules that differ by the relative spin of their nuclei. In the orthohydrogen form, the spins of the two protons are parallel and form a triplet state with a molecular spin quantum number of 1 (1⁄2+1⁄2); in the parahydrogen form the spins are antiparallel and form a singlet with a molecular spin quantum number of 0 (1⁄2–1⁄2). At standard temperature and pressure, hydrogen gas contains about 25% of the para form and 75% of the ortho form, also known as the "normal form". The equilibrium ratio of orthohydrogen to parahydrogen depends on temperature, but because the ortho form is an excited state and has a higher energy than the para form, it is unstable and cannot be purified. At very low temperatures, the equilibrium state is composed almost exclusively of the para form. The liquid and gas phase thermal properties of pure parahydrogen differ significantly from those of the normal form because of differences in rotational heat capacities, as discussed more fully in spin isomers of hydrogen. The ortho/para distinction also occurs in other hydrogen-containing molecules or functional groups, such as water and methylene, but is of little significance for their thermal properties.
The uncatalyzed interconversion between para and ortho H2 increases with increasing temperature; thus rapidly condensed H2 contains large quantities of the high-energy ortho form that converts to the para form very slowly. The ortho/para ratio in condensed H2 is an important consideration in the preparation and storage of liquid hydrogen: the conversion from ortho to para is exothermic and produces enough heat to evaporate some of the hydrogen liquid, leading to loss of liquefied material. Catalysts for the ortho-para interconversion, such as ferric oxide, activated carbon, platinized asbestos, rare earth metals, uranium compounds, chromic oxide, or some nickel compounds, are used during hydrogen cooling.
While H2 is not very reactive under standard conditions, it does form compounds with most elements. Hydrogen can form compounds with elements that are more electronegative, such as halogens (e.g., F, Cl, Br, I), or oxygen; in these compounds hydrogen takes on a partial positive charge. When bonded to fluorine, oxygen, or nitrogen, hydrogen can participate in a form of medium-strength noncovalent bonding with other similar molecules between their hydrogens called hydrogen bonding, which is critical to the stability of many biological molecules. Hydrogen also forms compounds with less electronegative elements, such as the metals and metalloids, in which it takes on a partial negative charge. These compounds are often known as hydrides.
Hydrogen forms a vast array of compounds with carbon called the hydrocarbons, and an even vaster array with heteroatoms that, because of their general association with living things, are called organic compounds. The study of their properties is known as organic chemistry and their study in the context of living organisms is known as biochemistry. By some definitions, "organic" compounds are only required to contain carbon. However, most of them also contain hydrogen, and because it is the carbon-hydrogen bond which gives this class of compounds most of its particular chemical characteristics, carbon-hydrogen bonds are required in some definitions of the word "organic" in chemistry. Millions of hydrocarbons are known, and they are usually formed by complicated synthetic pathways, which seldom involve elementary hydrogen.