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Epoch (astronomy)

In astronomy, an epoch is a moment in time used as a reference point for some time-varying astronomical quantity, such as the celestial coordinates or elliptical orbital elements of a celestial body, because these are subject to perturbations and vary with time. These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or aphelion of its orbit, or the size of the major axis of its orbit; the main use of astronomical quantities specified in this way is to calculate other relevant parameters of motion, in order to predict future positions and velocities. The applied tools of the disciplines of celestial mechanics or its subfield orbital mechanics can be used to generate an ephemeris, a table of values giving the positions and velocities of astronomical objects in the sky at a given time or times. Astronomical quantities can be specified in any of several ways, for example, as a polynomial function of the time-interval, with an epoch as a temporal point of origin.

Alternatively, the time-varying astronomical quantity can be expressed as a constant, equal to the measure that it had at the epoch, leaving its variation over time to be specified in some other way—for example, by a table, as was common during the 17th and 18th centuries. The word epoch was used in a different way in older astronomical literature, e.g. during the 18th century, in connection with astronomical tables. At that time, it was customary to denote as "epochs", not the standard date and time of origin for time-varying astronomical quantities, but rather the values at that date and time of those time-varying quantities themselves. In accordance with that alternative historical usage, an expression such as'correcting the epochs' would refer to the adjustment by a small amount, of the values of the tabulated astronomical quantities applicable to a fixed standard date and time of reference. Astronomical data are specified not only in their relation to an epoch or date of reference but in their relations to other conditions of reference, such as coordinate systems specified by "equinox", or "equinox and equator", or "equinox and ecliptic" – when these are needed for specifying astronomical data of the considered type.

When the data are dependent for their values on a particular coordinate system, the date of that coordinate system needs to be specified directly or indirectly. Celestial coordinate systems most used in astronomy are equatorial coordinates and ecliptic coordinates; these are defined relative to the vernal equinox position, which itself is determined by the orientations of the Earth's rotation axis and orbit around the Sun. Their orientations vary, there is an infinity of such coordinate systems possible, thus the coordinate systems most used in astronomy need their own date-reference because the coordinate systems of that type are themselves in motion, e.g. by the precession of the equinoxes, nowadays resolved into precessional components, separate precessions of the equator and of the ecliptic. The epoch of the coordinate system need not be the same, in practice is not the same, as the epoch for the data themselves; the difference between reference to an epoch alone, a reference to a certain equinox with equator or ecliptic, is therefore that the reference to the epoch contributes to specifying the date of the values of astronomical variables themselves.

The equinox with equator/ecliptic of a given date defines. Most standard coordinates in use today refer to 2000 TT, which occurred about 64 seconds sooner than noon UT1 on the same date. Before about 1984, coordinate systems dated to 1950 or 1900 were used. There is a special meaning of the expression "equinox of date"; when coordinates are expressed as polynomials in time relative to a reference frame defined in this way, that means the values obtained for the coordinates in respect of any interval t after the stated epoch, are in terms of the coordinate system of the same date as the obtained values themselves, i.e. the date of the coordinate system is equal to. It can be seen that the date of the coordinate system need not be the same as the epoch of the astronomical quantities themselves, but in that case, two dates will be associated with the data: one date is the epoch for the time-dependent expressions giving the values, the other date is that of the coordinate system in which the values are expressed.

For example, orbital elements osculating elements for minor planets, are given with reference to two dates: first, relative to a recent epoch for all of the elements: but some of the data are dependent on a chosen coordinate system, it is usual to specify the coordinate system of a standard epoch, not the same as the epoch of the data. An exam

Laurence Durlacher

Admiral Sir Laurence George Durlacher KCB OBE DSC was a Royal Navy officer who went on to be Fifth Sea Lord. Durlacher chose to specialise in signals, he served in World War II as Commander of HM Signal School at the Admiralty and as Fleet Signals Officer on the staff of Admiral Andrew Cunningham during the campaigns in North Africa and Italy. He was awarded the Legion of Merit by the US Government for his services in these campaigns and given command of HMS Volage in the Eastern Fleet in 1944. After the War, having been promoted to Captain in 1945, he became Deputy Director at the Admiralty Signal Division and, in 1949, was appointed Commander of the 3rd Destroyer Flotilla in the Mediterranean Fleet, he went on to be Commander of the Admiralty Signals and Radar Establishment at Haslemere in 1950 and Chief of Staff to the Commander-in-Chief, Eastern Fleet in 1952 before becoming Deputy Chief of Naval Personnel at the Admiralty in 1955. He was made Flag Officer commanding 5th Cruiser Squadron and Flag Officer Second in Command Far East Fleet in 1957 and Deputy Chief of the Naval Staff and Fifth Sea Lord in 1959.

In 1934 he married Rimma who went on to become a pillar of the British community on the Riviera

Rahul

Rahul, a popular male name in India, has a variety of meanings. The earliest meaning found in the Upanishads is "conqueror of all miseries". Rahul is Arabic for "traveler". Buddha's son was called Rahul, meaning "relation". Another meaning of Rahul is "offspring of lightning". Rahul Daulatrao Aher, Indian politician from Maharashtra Rahul Banerjee, Indian archer Rahul Banerjee, Indian Bengali actor Rahul Bhatt, Indian fitness trainer and actor Rahul Bheke, Indian footballer Rahul Bose, Indian Bengali actor, screenwriter, social activist Rahul Chandran, policy analyst Rahul Chahar, Indian cricketer Rahul Deshpande, Indian classical singer Rahul Dev, Indian actor and model Rahul Dev Burman, Indian composer and music director Rahul Dholakia, Indian film director and screenwriter Rahul Dravid, Indian cricketer Rahul Easwar, Indian author and activist Rahul Gandhi, Indian politician Rahul Kanwat, Indian cricketer K. L. Rahul, Indian cricketer Rahul Khanna, Indian Hindi actor Rahul Kumar, several people Rahul Madhav, Indian Malayalam actor Rahul Mahajan, Indian politician Rahul Mahajan, American blogger and author Rahul Mukerjee, Indian academic and statistician Rahul Nambiar, Indian singer Rahul Pandit, Indian physicist Rahul Potluri, Indian-British physician and researcher Rahul Prasad, several people Rahul Ram, Indian guitarist Rahul Ramakrishna,Indian actor and journalist Rahul Raj, Indian composer Rahul Rawail, Indian film director Rahul Roushan, Indian journalist and strategist Rahul Roy, Indian Hindi actor and model Rahul Roy, Indian accountant Rahul Saini, Indian author Rahul Sanghvi, Indian cricketer Rahul Sankrityayan, Indian historian, religious scholar, philosopher and polymath Rahul Sarpeshkar, American bioengineer Rahul Sharma, several people Rahul Singh, several people Rahul Sood, Canadian business executive Rahul Vaidya, Indian singer Rahul Yadav, Indian entrepreneur Rahul Yadav, Indian cricketer Rahul Yadav Chittaboina, Indian badminton player Rahula Raul Raoul Rasul

Giorgio Santelli

Maestro Giorgio Santelli was a fencer and fencing master, part of the Italian team that won the gold medal in Men's team sabre at the 1920 Summer Olympics and was the largest mid-20th century influence in raising the quality and popularity of fencing in the United States, creator of one of the best-known fencing equipment manufacturers. Born in Budapest, but always keeping his Italian citizenship, Giorgio was the son of Italo Santelli, a renowned fencing master from Italy who revolutionized sabre technique and was called the "Father of Modern Sabre Fencing". Giorgio was an Olympian in 1920, he won the Austrian and Italian sabre championships, the Austrian and Hungarian foil championships—equivalent to winning the Olympics in two different weapons. Santelli fought and won a famous duel with Adolfo Cotronei, arising out of an Olympic fencing dispute between his Italian father, who drove the Hungarian team, the leader of the Italian team. Maestro Santelli immigrated to the U. S. in 1924. He taught his art at the New York Athletic Club, before founding Salle Santelli in New York City.

Giorgio was US National Coach for several decades, U. S. Olympic Coach in 1928, 1932, 1936, 1948, 1952, he trained many national team members and champions from the 1940s through the 1980s, teaching champions and prominent fencers including George Worth, Tibor Nyilas, George Kolombatovich, Allan Kwartler, Neil Lazar, Uriah Jones, Robert Russell, Anne O'Donnell Russell, Marty Lang, Denise O'Connor, Ed Ballinger, Israel Colon, Ernest Schmatolla, Maurice Kamhi, Andy Shaw, Ed Wright, many others. Others who fenced at Salle Santelli included Olympians Norman Lewis, Robert Blum, Ralph Goldstein, Albert Axelrod, Zaddick Longenbach. In 1934, he established the United States Fencing Equipment Company, renamed in 1955 to George Santelli, Inc; this was one of the most known 20th century fencing supply houses in the United States. Santelli tirelessly and generously promoted fencing in all aspects, including stage choreography on Broadway and providing free instruction to high school fencers. Giorgio generously supported fencing masters coming to the United States, giving them a place to teach until they established their own schools, including great maestros such as Csaba Elthes.

Santelli made a unique contribution by tearing down the color barrier that existed in what had been a patrician sport, inviting black fencers to his club at a time when fencing had been a segregated activity, producing Olympians and national champions such as Uriah Jones, Ed Ballinger, Ed Wright. Santelli was inducted into the USFA Hall of Fame in 1963. A resident of Leonia, New Jersey, he died on October 8, 1985, in nearby Teaneck, at the age of 87. Fencing USFA USFA Hall of Fame Giorgio Santelli and Csaba Elthes - 2 Great Fencing Masters at the Wayback Machine Old Master of a Quick and Subtle Art Lessons from Santelli Giorgio Santelli at the Internet Broadway Database

Glenn Springs Historic District

Glenn Springs Historic District is a national historic district located at Glenn Springs, Spartanburg County, South Carolina. It encompasses 18 contributing buildings and 3 contributing sites in the historic health resort of Glenn Springs; the community developed as a resort around the mineral springs between about 1840 and 1940. The district includes several residences, two boarding houses, Cates House Ruins, Calvary Protestant Episcopal Church, Presbyterian Church, Cates Store, Glenn Springs Post Office, a pavilion, a cemetery, the site of the Glenn Springs Hotel, it includes notable buildings in the Greek Revival, Gothic Revival, Queen Anne, Bungalow styles. It was listed on the National Register of Historic Places in 1982

Goniobranchus geminus

Goniobranchus geminus known as the gem sea slug, is a species of colourful sea slug, a dorid nudibranch, a marine gastropod mollusc in the family Chromodorididae. Until 2012 this species was known as Chromodoris geminus but was moved to the genus Goniobranchus as a result of a molecular study. Goniobranchus geminus can reach a maximum size of 5 cm in length, it has four distinctive coloured lines around the mantle edge. Starting from a thin white outer line a light grayish line, followed by another white line and a bright golden yellow line; the background coloration from the back is light brown to yellowish speckled with mauve ocelli circled with a white margin. The foot and with a white margin has ocelli; the rhinophores are yellow or purple and laminated, gills are white. This sea slug lives in the Indian Ocean from Kenya to Sri Lanka and in the Red Sea and has a predilection for the external slopes of coral reefs. Goniobranchus kuniei. Goniobranchus leopardus. Hypselodoris tryoni. Goniobranchus tritos.

Photos of Goniobranchus geminus on Sealife Collection