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David Gill (astronomer)
Sir David Gill (12 June 1843 – 24 January 1914) was a Scottish astronomer who is known for measuring astronomical distances, for astrophotography and geodesy. He spent much of his career in South Africa. Life and work David Gill was born at 48 Skene Terrace in Aberdeen the son of David Gill, watchmaker and his wife Margaret Mitchell. He was educated first at Bellevue Academy in Aberdeen then at Dollar Academy. He spent two years at Aberdeen University, where he was taught by James Clerk Maxwell, and then joined his father's clock-making business. His most important influence at university was probably from Prof David Thomson. In 1863 they jointly repaired the university clock and both set up a new mechanical telescope at the Cromwell Tower Observatory. This was his introduction to astronomy. It would seem that Gill's interests lay elsewhere since after a few years he sold the business, and then spent time equipping Lord Lindsay's private observatory at Dun Echt, Aberd ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aberdeen
Aberdeen ( ; ; ) is a port city in North East Scotland, and is the List of towns and cities in Scotland by population, third most populous Cities of Scotland, Scottish city. Historically, Aberdeen was within the historic county of Aberdeenshire (historic), Aberdeenshire, but is now separate from the council area of Aberdeenshire. Aberdeen City Council is one of Scotland's 32 Local government in Scotland, local authorities (commonly referred to as ''councils''). Aberdeen has a population of for the main urban area and for the wider List of towns and cities in Scotland by population#Settlements, settlement including outlying localities, making it the United Kingdom's List of urban areas in the United Kingdom, 39th most populous built-up area. Aberdeen has a long, sandy coastline and features an oceanic climate, with cool summers and mild, rainy winters. Aberdeen received royal burgh status from David I of Scotland (1124–1153), which transformed the city economically. The tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
James Clerk Maxwell
James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish physicist and mathematician who was responsible for the classical theory of electromagnetic radiation, which was the first theory to describe electricity, magnetism and light as different manifestations of the same phenomenon. Maxwell's equations for electromagnetism achieved the Unification (physics)#Unification of magnetism, electricity, light and related radiation, second great unification in physics, where Unification (physics)#Unification of gravity and astronomy, the first one had been realised by Isaac Newton. Maxwell was also key in the creation of statistical mechanics. With the publication of "A Dynamical Theory of the Electromagnetic Field" in 1865, Maxwell demonstrated that electric force, electric and magnetic fields travel through space as waves moving at the speed of light. He proposed that light is an undulation in the same medium that is the cause of electric and magnetic phenomena. (Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphical), foreshortening, nearby objects show a larger parallax than farther objects, so parallax can be used to determine distances. To measure large distances, such as the distance of a planet or a star from Earth, astronomers use the principle of parallax. Here, the term ''Stellar parallax, parallax'' is the semi-angle of inclination between two sight-lines to the star, as observed when Earth is on opposite sides of the Sun in its orbit. These distances form the lowest rung of what is called "the cosmic distance ladder", the first in a succession of methods by which astronomers determine the distances to celestial objects, serving as a basis for other distance measurements in astronomy forming the higher rungs of the ladder. Because parallax ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Robert T
The name Robert is an ancient Germanic given name, from Proto-Germanic "fame" and "bright" (''Hrōþiberhtaz''). Compare Old Dutch ''Robrecht'' and Old High German ''Hrodebert'' (a compound of '' Hruod'' () "fame, glory, honour, praise, renown, godlike" and ''berht'' "bright, light, shining"). It is the second most frequently used given name of ancient Germanic origin.Reaney & Wilson, 1997. ''Dictionary of English Surnames''. Oxford University Press. It is also in use as a surname. Another commonly used form of the name is Rupert. After becoming widely used in Continental Europe, the name entered England in its Old French form ''Robert'', where an Old English cognate form (''Hrēodbēorht'', ''Hrodberht'', ''Hrēodbēorð'', ''Hrœdbœrð'', ''Hrœdberð'', ''Hrōðberχtŕ'') had existed before the Norman Conquest. The feminine version is Roberta. The Italian, Portuguese, and Spanish form is Roberto. Robert is also a common name in many Germanic languages, including En ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heliometer
A heliometer (from Greek ἥλιος ''hḗlios'' "sun" and ''measure'') is an instrument originally designed for measuring the variation of the Sun's diameter at different seasons of the year, but applied now to the modern form of the instrument which is capable of much wider use. Description The basic concept is to introduce a split element into a telescope's optical path so as to produce a double image. If one element is moved using a screw micrometer, precise angle measurements can be made. The simplest arrangement is to split the object lens in half, with one half fixed and the other attached to the micrometer screw and slid along the cut diameter. To measure the diameter of the Sun, for example, the micrometer is first adjusted so that the two images of the solar disk coincide (the "zero" position where the split elements form essentially a single element). The micrometer is then adjusted so that diametrically opposite sides of the two images of the solar disk just touc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Parallax
The most important fundamental distance measurements in astronomy come from trigonometric parallax, as applied in the '' stellar parallax method''. As the Earth orbits the Sun, the position of a nearby star will appear to shift slightly against the more distant background. This shift is the apex angle in an isosceles triangle, with 2 AU (the distance between the extreme positions of Earth's orbit around the Sun) making the base leg of the triangle and the distance to the star being the long equal-length legs (because of a very long distance from the Earth orbit to the observed star). The amount of shift is quite small, even for the nearest stars, measuring 1 arcsecond for an object at 1 parsec's distance (3.26 light-years), and thereafter decreasing in angular amount as the distance increases. Astronomers usually express distances in units of '' parsecs'' (parallax arcseconds); light-years are used in popular media. Because parallax becomes smaller for a greater stellar distan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cape Observatory
The South African Astronomical Observatory (SAAO) is the national centre for optical and infrared astronomy in South Africa. It was established in 1972. The observatory is run by the National Research Foundation of South Africa. The facility's function is to conduct research in astronomy and astrophysics. The primary telescopes are located in Sutherland, Northern Cape, Sutherland, which is from Observatory, Cape Town, where the headquarters is located. The SAAO has links worldwide for scientific and technological collaboration. Instrumental contributions from the South African Astronomical Observatory include the development of a spherical aberration corrector and the Southern African Large Telescope (SALT). The Noon Gun on Cape Town's Signal Hill (Cape Town), Signal Hill is fired remotely by a time signal from the Observatory. History The history of the SAAO began when the Royal Observatory, Cape of Good Hope, Royal Observatory at the Cape of Good Hope was founded in 1820 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mars
Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmospheric pressure is a few thousandths of Earth's, atmospheric temperature ranges from and cosmic radiation is high. Mars retains some water, in the ground as well as thinly in the atmosphere, forming cirrus clouds, frost, larger polar regions of permafrost and ice caps (with seasonal snow), but no liquid surface water. Its surface gravity is roughly a third of Earth's or double that of the Moon. It is half as wide as Earth or twice the Moon, with a diameter of , and has a surface area the size of all the dry land of Earth. Fine dust is prevalent across the surface and the atmosphere, being picked up and spread at the low Martian gravity even by the weak wind of the tenuous atmosphere. The terrain of Mars roughly follows a north-south ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ascension Island
Ascension Island is an isolated volcanic island, 7°56′ south of the Equator in the Atlantic Ocean, South Atlantic Ocean. It is about from the coast of Africa and from the coast of South America. It is governed as part of the British Overseas Territories, British Overseas Territory of Saint Helena, Ascension and Tristan da Cunha, of which the main island, Saint Helena, is around to the southeast. The territory also includes the sparsely populated Tristan da Cunha archipelago, to the south, about halfway to the Antarctic Circle. The discovery of Ascension by Joao da Nova in 1501 was described by two Portuguese chroniclers who probably misnamed it as Conception Island. The popular idea that Ascension was rediscovered by Afonso de Albuquerque in 1503 is probably wrong, Ascension having been long confused with Trindade and Martim Vaz, Trindade. Ascension Island was garrisoned by the British Admiralty from 22 October 1815 to 1922 and was an important refueling stop for ships a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transit Of Venus
A transit of Venus takes place when Venus passes directly between the Sun and the Earth (or any other superior planet), becoming visible against (and hence obscuring a small portion of) the solar disk. During a transit, Venus is visible as a small black circle moving across the face of the Sun. Transits of Venus reoccur periodically. A pair of transits takes place eight years apart in December (Gregorian calendar) followed by a gap of 121.5 years, before another pair occurs eight years apart in June, followed by another gap, of 105.5 years. The dates advance by about two days per 243-year cycle. The periodicity is a reflection of the fact that the orbital periods of Earth and Venus are close to 8:13 and 243:395 commensurabilities. The last pairs of transits occurred on 8 June 2004 and 5–6 June 2012. The next pair of transits will occur on 10–11 December 2117 and 8 December 2125. Transits of Venus were in the past used to determine the size of the Solar System. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mauritius
Mauritius, officially the Republic of Mauritius, is an island country in the Indian Ocean, about off the southeastern coast of East Africa, east of Madagascar. It includes the main island (also called Mauritius), as well as Rodrigues, Agaléga, and St. Brandon (Cargados Carajos shoals). The islands of Mauritius and Rodrigues, along with nearby Réunion (a French overseas department), are part of the Mascarene Islands. The main island of Mauritius, where the population is concentrated, hosts the capital and largest city, Port Louis. The country spans and has an exclusive economic zone covering approximately . The 1502 Portuguese Cantino planisphere has led some historians to speculate that Arab sailors were the first to discover the uninhabited island around 975, naming it ''Dina Arobi''. Called ''Ilha do Cirne'' or ''Ilha do Cerne'' on early Portuguese maps, the island was visited by Portuguese sailors in 1507. A Dutch fleet, under the command of Admiral Van War ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aberdeenshire (historic)
Aberdeenshire or the County of Aberdeen (, ) is a Shires of Scotland, historic county in Scotland. The county gives its name to the modern Aberdeenshire Council areas of Scotland, council area, which covers a larger area than the historic county. The historic county ceased to be used for local government purposes in 1975, but its boundaries are still used for certain functions, being a registration county. The area of the historic county excluding the Aberdeen City council area is also a Lieutenancy areas of Scotland, lieutenancy area. The area is generally hilly. The south-west of the county includes part of the Grampian Mountains. The historic county borders Kincardineshire, County of Angus, Angus and Perthshire to the south, Inverness-shire and Banffshire to the west, and the North Sea to the north and east. History Early history The area which would become Aberdeenshire was anciently occupied by the Picts, whom Claudius Ptolemy, Ptolemy, writing , called Taexali. There is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
