1.
12-hour clock
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The 12-hour clock is a time convention in which the 24 hours of the day are divided into two periods, a. m. and p. m. Each period consists of 12 hours numbered,12,1,2,3,4,5,6,7,8,9,10, and 11. The 24 hour/day cycle starts at 12 midnight, runs through 12 noon, the 12-hour clock was developed over time from the mid-second millennium BC to the 16th century AD. The natural day- and night division of a calendar day forms the basis as to why each day is split into two cycles. Originally there were two cycles, one cycle which could be tracked by the position of the Sun followed by one cycle which could be tracked by the Moon and this would eventually evolve into the two 12-hour periods that started at midnight and noon which are used today. Noon itself is rarely abbreviated today, but if it is, the 12-hour clock can be traced back as far as Mesopotamia and Ancient Egypt. Both an Egyptian sundial for daytime use and an Egyptian water clock for night-time use were found in the tomb of Pharaoh Amenhotep I, dating to c.1500 BC, these clocks divided their respective times of use into 12 hours each. The Romans also used a 12-hour clock, daylight was divided into 12 equal hours, in Northern Europe these dials generally used the 12-hour numbering scheme in Roman numerals, but showed both a. m. and p. m. periods in sequence. This is known as the system, and can be seen on many surviving clock faces, such as those at Wells. Elsewhere in Europe, particularly in Italy, numbering was more likely to be based on the 24-hour system, the 12-hour clock was used throughout the British empire. During the 15th and 16th centuries, the 12-hour analog dial, the 24-hour analog dial was reserved for more specialized applications, such as astronomical clocks and chronometers. Most analog clocks and watches use the 12-hour dial, on which the shorter hour hand rotates once every 12 hours. Some analog clock dials have a ring of numbers along with the standard 1-to-12 numbered ring. The number 12 is paired either with a 00 or a 24, while the numbers 1 through 11 are paired with the numbers 13 through 23 and this modification allows the clock to be read also in the 24-hour notation. This kind of 12-hour clock can be found in countries where the 24-hour clock is preferred, in several countries the 12-hour clock is the dominant written and spoken system of time. Other countries use the 12-hour clock mainly in spoken time, while the 24-hour notation is written, in most countries the 12-hour clock is used in speech alongside the 24-hour clock. The 12-hour clock in speech often uses such as in the morning, in the afternoon, in the evening. Outside of English-speaking countries, the terms a. m. and p. m. are seldom used and often unknown
2.
Meridian (geography)
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A meridian is the half of an imaginary great circle on the Earths surface, terminated by the North Pole and the South Pole, connecting points of equal longitude. The position of a point along the meridian is given by its latitude indicating how many degrees north or south of the Equator the point is, each meridian is perpendicular to all circles of latitude. Each is also the length, being half of a great circle on the Earths surface. Most maps show the lines of longitude, the position of the prime meridian has changed a few times throughout history, mainly due to the transit observatory being built next door to the previous one. Such changes had no significant practical effect, historically, the average error in the determination of longitude was much larger than the change in position. The adoption of WGS84 as the system has moved the geodetic prime meridian 102.478 metres east of its last astronomic position. The position of the current geodetic prime meridian is not identified at all by any kind of sign or marking in Greenwich, but can be located using a GPS receiver. The term meridian comes from the Latin meridies, meaning midday, the same Latin stem gives rise to the terms a. m. and p. m. used to disambiguate hours of the day when utilizing the 12-hour clock. Therefore, a compass needle will be parallel to the magnetic meridian, the angle between the magnetic and the true meridian is the magnetic declination, which is relevant for navigating with a compass. Searchable PDF prepared by the author, C. A. White, resources page of the U. S. Department of the Interior, Bureau of Land Management Meridian
3.
Prime meridian
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A prime meridian is a meridian in a geographical coordinate system at which longitude is defined to be 0°. Together, a meridian and its antimeridian form a great circle. This great circle divides the sphere, e. g. the Earth, if one uses directions of East and West from a defined prime meridian, then they can be called Eastern Hemisphere and Western Hemisphere. The most widely used modern meridian is the IERS Reference Meridian and it is derived but deviates slightly from the Greenwich Meridian, which was selected as an international standard in 1884. The notion of longitude was developed by the Greek Eratosthenes in Alexandria, and Hipparchus in Rhodes, but it was Ptolemy who first used a consistent meridian for a world map in his Geographia. The main point is to be comfortably west of the tip of Africa as negative numbers were not yet in use. His prime meridian corresponds to 18°40 west of Winchester today, at that time the chief method of determining longitude was by using the reported times of lunar eclipses in different countries. Ptolemys Geographia was first printed with maps at Bologna in 1477, but there was still a hope that a natural basis for a prime meridian existed. The Tordesillas line was settled at 370 leagues west of Cape Verde. This is shown in Diogo Ribeiros 1529 map, in 1541, Mercator produced his famous 41 cm terrestrial globe and drew his prime meridian precisely through Fuertaventura in the Canaries. His later maps used the Azores, following the magnetic hypothesis, but by the time that Ortelius produced the first modern atlas in 1570, other islands such as Cape Verde were coming into use. In his atlas longitudes were counted from 0° to 360°, not 180°W to 180°E as is usual today and this practice was followed by navigators well into the 18th century. In 1634, Cardinal Richelieu used the westernmost island of the Canaries, Ferro, 19°55 west of Paris, the geographer Delisle decided to round this off to 20°, so that it simply became the meridian of Paris disguised. In the early 18th century the battle was on to improve the determination of longitude at sea, between 1765 and 1811, Nevil Maskelyne published 49 issues of the Nautical Almanac based on the meridian of the Royal Observatory, Greenwich. Maskelynes tables not only made the lunar method practicable, they made the Greenwich meridian the universal reference point. In 1884, at the International Meridian Conference in Washington, D. C.22 countries voted to adopt the Greenwich meridian as the meridian of the world. The French argued for a line, mentioning the Azores and the Bering Strait. In October 1884 the Greenwich Meridian was selected by delegates to the International Meridian Conference held in Washington, united States to be the common zero of longitude and standard of time reckoning throughout the world
4.
Great circle
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A great circle, also known as an orthodrome or Riemannian circle, of a sphere is the intersection of the sphere and a plane that passes through the center point of the sphere. This partial case of a circle of a sphere is opposed to a circle, the intersection of the sphere. Any diameter of any great circle coincides with a diameter of the sphere, and therefore all great circles have the same circumference as each other, a great circle is the largest circle that can be drawn on any given sphere. Every circle in Euclidean 3-space is a circle of exactly one sphere. For most pairs of points on the surface of a sphere, there is a great circle through the two points. The exception is a pair of points, for which there are infinitely many great circles. The minor arc of a circle between two points is the shortest surface-path between them. In this sense, the arc is analogous to “straight lines” in Euclidean geometry. The length of the arc of a great circle is taken as the distance between two points on a surface of a sphere in Riemannian geometry. The great circles are the geodesics of the sphere, in higher dimensions, the great circles on the n-sphere are the intersection of the n-sphere with 2-planes that pass through the origin in the Euclidean space Rn+1. To prove that the arc of a great circle is the shortest path connecting two points on the surface of a sphere, one can apply calculus of variations to it. Consider the class of all paths from a point p to another point q. Introduce spherical coordinates so that p coincides with the north pole. Any curve on the sphere that does not intersect either pole, except possibly at the endpoints, can be parametrized by θ = θ, ϕ = ϕ, a ≤ t ≤ b provided we allow φ to take on arbitrary real values. The infinitesimal arc length in these coordinates is d s = r θ ′2 + ϕ ′2 sin 2 θ d t. So the length of a curve γ from p to q is a functional of the curve given by S = r ∫ a b θ ′2 + ϕ ′2 sin 2 θ d t. Note that S is at least the length of the meridian from p to q, S ≥ r ∫ a b | θ ′ | d t ≥ r | θ − θ |. Since the starting point and ending point are fixed, S is minimized if and only if φ =0, so the curve must lie on a meridian of the sphere φ = φ0 = constant
5.
Eastern Hemisphere
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The Eastern Hemisphere is a geographical term for the half of the earth that is east of the prime meridian and west of the antimeridian. It is also used to refer to Europe, Asia, Africa, and Australia, in contrast with the Western Hemisphere and this hemisphere may also be called the Oriental Hemisphere. In addition, it may be used in a cultural or geopolitical sense as a synonym for the Old World, the line demarcating the Eastern and Western Hemispheres is an arbitrary convention, unlike the Equator which divides the Northern and Southern Hemispheres. The prime meridian at 0° longitude and the antimeridian, at 180° longitude are the accepted boundaries. Prior to the adoption of standard time, numerous prime meridians were decreed by various countries where time was defined by local noon. The center of the Eastern Hemisphere is located in the Indian Ocean at the intersection of the equator, the land mass of the Eastern Hemisphere is larger than that of the Western Hemisphere and has a wide variety of habitats. 82% of humans live in the Eastern Hemisphere, compared to 18% in Western Hemisphere, media related to Eastern Hemisphere at Wikimedia Commons
6.
Pacific Ocean
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The Pacific Ocean is the largest and deepest of the Earths oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean in the south and is bounded by Asia and Australia in the west, the Mariana Trench in the western North Pacific is the deepest point in the world, reaching a depth of 10,911 metres. Both the center of the Water Hemisphere and the Western Hemisphere are in the Pacific Ocean, the oceans current name was coined by Portuguese explorer Ferdinand Magellan during the Spanish circumnavigation of the world in 1521, as he encountered favourable winds on reaching the ocean. He called it Mar Pacífico, which in both Portuguese and Spanish means peaceful sea, important human migrations occurred in the Pacific in prehistoric times. Long-distance trade developed all along the coast from Mozambique to Japan, trade, and therefore knowledge, extended to the Indonesian islands but apparently not Australia. By at least 878 when there was a significant Islamic settlement in Canton much of trade was controlled by Arabs or Muslims. In 219 BC Xu Fu sailed out into the Pacific searching for the elixir of immortality, from 1404 to 1433 Zheng He led expeditions into the Indian Ocean. The east side of the ocean was discovered by Spanish explorer Vasco Núñez de Balboa in 1513 after his expedition crossed the Isthmus of Panama and he named it Mar del Sur because the ocean was to the south of the coast of the isthmus where he first observed the Pacific. Later, Portuguese explorer Ferdinand Magellan sailed the Pacific East to West on a Castilian expedition of world circumnavigation starting in 1519, Magellan called the ocean Pacífico because, after sailing through the stormy seas off Cape Horn, the expedition found calm waters. The ocean was often called the Sea of Magellan in his honor until the eighteenth century, sailing around and east of the Moluccas, between 1525 and 1527, Portuguese expeditions discovered the Caroline Islands, the Aru Islands, and Papua New Guinea. In 1542–43 the Portuguese also reached Japan, in 1564, five Spanish ships consisting of 379 explorers crossed the ocean from Mexico led by Miguel López de Legazpi and sailed to the Philippines and Mariana Islands. The Manila galleons operated for two and a half centuries linking Manila and Acapulco, in one of the longest trade routes in history, Spanish expeditions also discovered Tuvalu, the Marquesas, the Cook Islands, the Solomon Islands, and the Admiralty Islands in the South Pacific. In the 16th and 17th century Spain considered the Pacific Ocean a Mare clausum—a sea closed to other naval powers, as the only known entrance from the Atlantic the Strait of Magellan was at times patrolled by fleets sent to prevent entrance of non-Spanish ships. On the western end of the Pacific Ocean the Dutch threatened the Spanish Philippines, Spain also sent expeditions to the Pacific Northwest reaching Vancouver Island in southern Canada, and Alaska. The French explored and settled Polynesia, and the British made three voyages with James Cook to the South Pacific and Australia, Hawaii, and the North American Pacific Northwest, one of the earliest voyages of scientific exploration was organized by Spain in the Malaspina Expedition of 1789–1794. It sailed vast areas of the Pacific, from Cape Horn to Alaska, Guam and the Philippines, New Zealand, Australia, and the South Pacific. Growing imperialism during the 19th century resulted in the occupation of much of Oceania by other European powers, and later, Japan, in Oceania, France got a leading position as imperial power after making Tahiti and New Caledonia protectorates in 1842 and 1853 respectively. After navy visits to Easter Island in 1875 and 1887, Chilean navy officer Policarpo Toro managed to negotiate an incorporation of the island into Chile with native Rapanui in 1888, by occupying Easter Island, Chile joined the imperial nations
7.
Russia
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Russia, also officially the Russian Federation, is a country in Eurasia. The European western part of the country is more populated and urbanised than the eastern. Russias capital Moscow is one of the largest cities in the world, other urban centers include Saint Petersburg, Novosibirsk, Yekaterinburg, Nizhny Novgorod. Extending across the entirety of Northern Asia and much of Eastern Europe, Russia spans eleven time zones and incorporates a range of environments. It shares maritime borders with Japan by the Sea of Okhotsk, the East Slavs emerged as a recognizable group in Europe between the 3rd and 8th centuries AD. Founded and ruled by a Varangian warrior elite and their descendants, in 988 it adopted Orthodox Christianity from the Byzantine Empire, beginning the synthesis of Byzantine and Slavic cultures that defined Russian culture for the next millennium. Rus ultimately disintegrated into a number of states, most of the Rus lands were overrun by the Mongol invasion. The Soviet Union played a role in the Allied victory in World War II. The Soviet era saw some of the most significant technological achievements of the 20th century, including the worlds first human-made satellite and the launching of the first humans in space. By the end of 1990, the Soviet Union had the second largest economy, largest standing military in the world. It is governed as a federal semi-presidential republic, the Russian economy ranks as the twelfth largest by nominal GDP and sixth largest by purchasing power parity in 2015. Russias extensive mineral and energy resources are the largest such reserves in the world, making it one of the producers of oil. The country is one of the five recognized nuclear weapons states and possesses the largest stockpile of weapons of mass destruction, Russia is a great power as well as a regional power and has been characterised as a potential superpower. The name Russia is derived from Rus, a state populated mostly by the East Slavs. However, this name became more prominent in the later history, and the country typically was called by its inhabitants Русская Земля. In order to distinguish this state from other states derived from it, it is denoted as Kievan Rus by modern historiography, an old Latin version of the name Rus was Ruthenia, mostly applied to the western and southern regions of Rus that were adjacent to Catholic Europe. The current name of the country, Россия, comes from the Byzantine Greek designation of the Kievan Rus, the standard way to refer to citizens of Russia is Russians in English and rossiyane in Russian. There are two Russian words which are translated into English as Russians
Kiribati;
New Zealand;
