Royal Observatory, Greenwich

The historic prime meridian or Greenwich meridian is a geographical reference line that passes through the Royal Observatory, Greenwich, in London, England. The modern IERS Reference Meridian widely used today is based on the Greenwich meridian, but differs slightly from it. The prime meridian was first established by Sir George Airy in 1851, and by 1884, over two-thirds of all ships and tonnage used it as the reference meridian on their charts and maps. In October of that year, at the behest of US President Chester A. Arthur, 41 delegates from 25 nations met in Washington, D.C., United States, for the International Meridian Conference. This conference selected the meridian passing through Greenwich as the official prime meridian due to its popularity. However, France abstained from the vote, and French maps continued to use the Paris meridian for several decades. In the 18th century, London lexicographer Malachy Postlethwayt published his African maps showing the "Meridian of London" intersecting the Equator a few degrees west of the later meridian and Accra, Ghana. The plane of the prime meridian is parallel to the local gravity vector at the Airy transit circle (51°28′40.1″N 0°0′5.3″W) of the Greenwich observatory. The prime meridian was therefore long symbolised by a brass strip in the courtyard, now replaced by stainless steel, and since 16 December 1999, it has been marked by a powerful green laser shining north across the London night sky. Global Positioning System (GPS) receivers show that the marking strip for the prime meridian at Greenwich is not exactly at zero degrees, zero minutes, and zero seconds but at approximately 5.3 seconds of arc to the west of the meridian (meaning that the meridian appears to be 102.478 metres east). In the past, this offset has been attributed to the establishment of reference meridians for space-based location systems such as WGS 84 (which GPS relies on) or that errors gradually crept into the International Time Bureau timekeeping process. The actual reason for the discrepancy is that the difference between precise GNSS coordinates and astronomically determined coordinates everywhere remains a localized gravity effect due to vertical deflection; thus, no systematic rotation of global longitudes occurred between the former astronomical system and the current geodetic system.

The Shepherd Gate Clock (51°28′41″N 0°00′05″W) is mounted on the wall outside the gate of the Royal Observatory, Greenwich building in Greenwich, Greater London. The clock, an early example of an electric clock, was a slave mechanism controlled by electric pulses transmitted by a master clock inside the main building. The network of master and slave clocks was constructed and installed by Charles Shepherd in 1852. The clock by the gate was probably the first to display Greenwich Mean Time to the public, and is unusual in using the 24-hour analog dial. Also it originally showed astronomical time which started at 12 noon not midnight. The gate clock distributed the time publicly; another time signal of the observatory was the time ball, since 1833. The time ball only signalled 1.00pm (13:00), but could be seen from afar. Eventually the idea of distributing time signals via wires led to more and more electrical distribution of time signals by this method. Time signals, besides from their general importance in the affairs of business, were especially important for running ships and trains punctually. The situation was exacerbated by a lack of accuracy in many clocks compared to modern time-keepers.

The Greenwich 28-inch refractor is a telescope at the Royal Observatory, Greenwich, where it was first installed in 1893. It is a 28-inch ( 71 cm) aperture objective lens telescope, otherwise known as a refractor, and was made by the telescope maker Sir Howard Grubb. The achromatic lens was made Grubb from Chance Brothers glass. The mounting is older however and dates to the 1850s, having been designed by Royal Observatory director George Airy and the firm Ransomes and Simms. The telescope is noted for its spherical dome which extends beyond the tower, nicknamed the "onion" dome. Another name for this telescope is "The Great Equatorial" which it shares with the building, which housed an older but smaller telescope previously.The telescope was re-commissioned by Queen Elizabeth II in May 1975 after it was brought back from Herstmonceux in Sussex. It was placed in the renovated original dome at Greenwich for the tricentennial celebration of the observatory.

Greenwich Castle was a hunting lodge used during the reign of Henry VIII, located in Greenwich Park, in Greenwich, England. The Royal Observatory, Greenwich now stands on the site. Greenwich Castle was apparently a favourite place for Henry VIII to house his mistresses, as it was within easy travelling distance of Greenwich Palace at the foot of the hill.The castle was previously known as Duke Humphrey's Tower after its builder, Humphrey, Duke of Gloucester, a younger brother of King Henry V.

The Peter Harrison Planetarium is a 120-seat digital laser planetarium, situated in Greenwich Park, London and is part of the National Maritime Museum. It opened on 25 May 2007.The planetarium uses Digistar 3 software with blue, red and green lasers and grating light valve (GLV) technology to create a 4,000 pixel strip. This strip is swept to produce a 5,000 by 4,000 pixel image, refreshed 60 times per second. The image is projected through a fisheye lens onto the dome of the planetarium.This planetarium is housed inside a 45-ton bronze-clad truncated cone, with the north side tilted at 51.5o to the horizontal (the latitude of Greenwich), the south side pointing at the local Zenith (i.e. at 90 degrees to the local horizon) and the top being slanted to be parallel to the celestial equator. The construction stands parallel to (but 50 metres east of) the prime meridian. It was conceived under the then Director, Roy Clare CBE, as the centrepiece of the "Time and Space" project, a £17.7m re-development of the Royal Observatory, Greenwich, and funded with a £3.25m grant from the Peter Harrison Foundation.

The Statue of Yuri Gagarin in Greenwich, London, is a zinc statue depicting the cosmonaut wearing a spacesuit and standing on top of a globe. The figure was originally unveiled on 14 July 2011 at a temporary location in the Mall, close to Admiralty Arch and facing the statue of Captain James Cook. It was later moved to the Royal Observatory, Greenwich, at a site overlooking the Prime Meridian line, and was unveiled at the new location on 7 March 2013. There had been an unsuccessful proposal to move it to Manchester.The 3.5-metre (11 ft) high statue is a replica of an original by Anatoly Novikov in Lyubertsy, where Gagarin was trained as a foundry worker. The statue was a gift to the British Council from the Russian space agency Roscosmos as a part of several cultural events commemorating the 50th anniversary of the first human spaceflight. The original location of the statue was chosen to be where Gagarin first met the then Prime Minister Harold Macmillan.

Greenwich Park is a former hunting park in Greenwich and one of the largest single green spaces in south-east London. One of the Royal Parks of London, and the first to be enclosed (in 1433), it covers 74 hectares (180 acres), and is part of the Greenwich World Heritage Site. It commands fine views over the River Thames, the Isle of Dogs and the City of London (Simon Jenkins rated the view of the Royal Hospital with Canary Wharf in the distance as one of the top ten in England).The park is open year-round. It is listed Grade I on the Register of Historic Parks and Gardens. In 2020, it was awarded a National Lottery grant to restore its historic features, build a learning centre, enhance the park's biodiversity, and provide better access for people with disabilities.

Greenwich ( (listen) GREN-itch, GRIN-ij, GRIN-itch, or GREN-ij) is a town in south-east London, England, located in the historic county of Kent and the ceremonial county of Greater London. It is situated 5.5 miles (8.9 km) east-southeast of Charing Cross. Greenwich is notable for its maritime history and for giving its name to the Greenwich Meridian (0° longitude) and Greenwich Mean Time. The town became the site of a royal palace, the Palace of Placentia from the 15th century, and was the birthplace of many Tudors, including Henry VIII and Elizabeth I. The palace fell into disrepair during the English Civil War and was demolished to be replaced by the Royal Naval Hospital for Sailors, designed by Sir Christopher Wren and his assistant Nicholas Hawksmoor. These buildings became the Royal Naval College in 1873, and they remained a military education establishment until 1998 when they passed into the hands of the Greenwich Foundation. The historic rooms within these buildings remain open to the public; other buildings are used by University of Greenwich and Trinity Laban Conservatoire of Music and Dance. The town became a popular resort in the 18th century and many grand houses were built there, such as Vanbrugh Castle (1717) established on Maze Hill, next to the park. From the Georgian period estates of houses were constructed above the town centre. The maritime connections of Greenwich were celebrated in the 20th century, with the siting of the Cutty Sark and Gipsy Moth IV next to the river front, and the National Maritime Museum in the former buildings of the Royal Hospital School in 1934. Historically an ancient parish in the Blackheath Hundred of Kent, the town formed part of the growing conurbation of London in the 19th century. When the County of London, an administrative area designed to replace the Metropolitan Board of Works, was formed in 1889, the parish merged with those of Charlton-next-Woolwich, Deptford St Nicholas and Kidbrooke to create the Metropolitan Borough of Greenwich. When local government in London was again reformed in 1965, it merged with most of the Metropolitan Borough of Woolwich, creating what is now the Royal Borough of Greenwich, a local authority district of Greater London.

The equestrian events at the 2012 Olympic Games in London were held between 28 July and 9 August at Greenwich Park. Medals were awarded in three disciplines for both individual and team competitions.Great Britain was the most successful nation, topping the medal table with three golds and five medals in total. They were particularly dominant in team events, taking two gold medals and a silver medal from three team events.

Queen Elizabeth's Oak was a veteran oak tree in Greenwich Park, London. Seeded in the 12th century, the tree formed part of the grounds of the Palace of Placentia, home to the Tudor royal family. Henry VIII is said to have danced around the tree with Anne Boleyn. Their daughter Elizabeth I, after whom the tree is named, is said to have picnicked beneath its canopy, or else within its hollow trunk. When the palace grounds became Greenwich Park, the hollow tree was used as a prison for criminals caught on the grounds. The tree died in the 19th century but was left standing, partly supported by ivy. It fell in a storm in June 1991 and has been left lying where it fell, protected by a fence and marked with a plaque.

Queen's House is a former royal residence built between 1616 and 1635 near Greenwich Palace, a few miles down-river from the City of London and now in the London Borough of Greenwich. It presently forms a central focus of what is now the Old Royal Naval College with a grand vista leading to the River Thames. Its architect was Inigo Jones, for whom it was a crucial early commission, for Anne of Denmark, the queen of King James VI and I. Queen's House is one of the most important buildings in British architectural history, being the first consciously classical building to have been constructed in the country. It was Jones's first major commission after returning from his 1613–1615 grand tour of Roman, Renaissance, and Palladian architecture in Italy. Some earlier English buildings, such as Longleat and Burghley House, had made borrowings from the classical style, but these were restricted to small details not applied in a systematic way, or the building may be a mix of different styles. Furthermore, the form of these buildings was not informed by an understanding of classical precedents. Queen's House would have appeared revolutionary to English eyes in its day. Jones is credited with the introduction of Palladianism with the construction of Queen's House, although it diverges from the mathematical constraints of Palladio, and it is likely that the immediate precedent for the H-shaped plan straddling a road is the Villa Medici at Poggio a Caiano by Giuliano da Sangallo. Today the building is both a Grade I listed building and a scheduled monument, a status that includes the 115-foot-wide (35 m), axial vista to the River Thames. The house now forms part of the National Maritime Museum and is used to display parts of its substantial collection of maritime paintings and portraits.

Ranger's House is a medium-sized red brick Georgian mansion in the Palladian style, adjacent to Greenwich Park in the south east of London. It is situated in Blackheath and backs directly onto Greenwich Park. Previously known as Chesterfield House, its current name is associated with the Ranger of Greenwich Park, a royal appointment; the house was the Ranger's official residence for most of the 19th century. It is a Grade I listed building. There is a rose garden behind it, and since 2002 it has housed the Wernher Collection of art.