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Nautical Time
Nautical time is a maritime time standard established in the 1920s to allow ships on high seas to coordinate their local time with other ships, consistent with a long nautical tradition of accurate celestial navigation. Nautical time divides the globe into 24 nautical time zones with hourly clock offsets, spaced at 15 degrees by longitudinal coordinate, with no political deviation. Nautical time keeping dates back to the early 20th century as a standard way to keep time at sea, although it largely only applied to military fleets pre–World War 2. This time-keeping method is only used for radio communications and to account for slight inaccuracies that using Greenwich Mean Time (GMT) may lead to during navigation of the high seas. It is typically only used for trans-oceanic travel, as captains will often not change the timekeeping for short distances such as channels or inland seas. History of nautical time Establishment The establishment of nautical standard times, nauti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time Standard
A time standard is a specification for measuring time: either the rate at which time passes or points in time or both. In modern times, several time specifications have been officially recognized as standards, where formerly they were matters of custom and practice. An example of a kind of time standard can be a time scale, specifying a method for measuring divisions of time. A standard for civil time can specify both time intervals and time-of-day. Standardized time measurements are made using a clock to count periods of some period changes, which may be either the changes of a natural phenomenon or of an artificial machine. Historically, time standards were often based on the Earth's rotational period. From the late 18 century to the 19th century it was assumed that the Earth's daily rotational rate was constant. Astronomical observations of several kinds, including eclipse records, studied in the 19th century, raised suspicions that the rate at which Earth rotates is gradua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sidereal Time
Sidereal time (as a unit also sidereal day or sidereal rotation period) (sidereal ) is a timekeeping system that astronomers use to locate celestial objects. Using sidereal time, it is possible to easily point a telescope to the proper coordinates in the night sky. In short, sidereal time is a "time scale that is based on Earth's rate of rotation measured relative to the fixed stars", or more correctly, relative to the March equinox. Viewed from the same location, a star seen at one position in the sky will be seen at the same position on another night at the same sidereal time. This is similar to how the time kept by a sundial ( Solar time) can be used to find the location of the Sun. Just as the Sun and Moon appear to rise in the east and set in the west due to the rotation of Earth, so do the stars. Both Solar time and sidereal time make use of the regularity of Earth's rotation about its polar axis: solar time following the Sun while, roughly speaking, sidereal time f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time Scales
Time scale may refer to: *Time standard, a specification of either the rate at which time passes, points in time, or both *A duration or quantity of time: **Orders of magnitude (time) as a power of 10 in seconds; **A specific unit of time * Geological time scale, a scale that divides up the history of Earth into scientifically meaningful periods In astronomy and physics: *Dynamical time scale, in stellar physics, the time in which changes in one part of a body can be communicated to the rest of that body, or in celestial mechanics, a realization of a time-like argument based on a dynamical theory *Nuclear timescale, an estimate of the lifetime of a star based solely on its rate of fuel consumption *Thermal time scale, an estimate of the lifetime of a star once the fuel reserves at its center are used up In cosmology and particle physics: * Planck time, the time scale beneath which quantum effects are comparable in significance to gravitational effects In mathematics: *Time-scale ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horology
Horology (; related to Latin '; ; , interfix ''-o-'', and suffix ''-logy''), . is the study of the measurement of time. Clocks, watches, clockwork, sundials, hourglasses, clepsydras, timers, time recorders, marine chronometers, and atomic clocks are all examples of instruments used to measure time. In current usage, horology refers mainly to the study of mechanical time-keeping devices, while chronometry more broadly includes electronic devices that have largely supplanted mechanical clocks for the best accuracy and precision in time-keeping. People interested in horology are called ''horologists''. That term is used both by people who deal professionally with timekeeping apparatuses (watchmakers, clockmakers), as well as aficionados and scholars of horology. Horology and horologists have numerous organizations, both professional associations and more scholarly societies. The largest horological membership organisation globally is the NAWCC, the National Association of Watc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meridians (geography)
Meridian or a meridian line (from Latin ''meridies'' via Old French ''meridiane'', meaning “midday”) may refer to Science * Meridian (astronomy), imaginary circle in a plane perpendicular to the planes of the celestial equator and horizon ** Central meridian (planets) * Meridian (geography), an imaginary arc on the Earth's surface from the North Pole to the South Pole ** Meridian arc, the distance between two points with the same longitude ** Prime meridian, origin of longitudes ** Principal meridian, arbitrary meridians used as references in land surveying * Meridian line, used with a gnomon to measure solar elevation and time of year * Autonomous sensory meridian response, a static-like or tingling sensation on the skin Places Cities and towns * Meridian, California (other), U.S., multiple California towns named Meridian * Meridian, Colorado, U.S. * Meridian, Florida, U.S. * Meridian, Georgia, U.S. * Meridian, Idaho, U.S. * Meridian, Mississippi, U.S. * Meri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solar Time
Solar time is a calculation of the passage of time based on the position of the Sun in the sky. The fundamental unit of solar time is the day, based on the synodic rotation period. Two types of solar time are apparent solar time (sundial time) and mean solar time (clock time). Introduction A tall pole vertically fixed in the ground casts a shadow on any sunny day. At one moment during the day, the shadow will point exactly north or south (or disappear when and if the Sun moves directly overhead). That instant is local apparent noon, or 12:00 local apparent time. About 24 hours later the shadow will again point north–south, the Sun seeming to have covered a 360-degree arc around Earth's axis. When the Sun has covered exactly 15 degrees (1/24 of a circle, both angles being measured in a plane perpendicular to Earth's axis), local apparent time is 13:00 exactly; after 15 more degrees it will be 14:00 exactly. The problem is that in September the Sun takes less time (as me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
British Admiralty
The Admiralty was a department of the Government of the United Kingdom responsible for the command of the Royal Navy until 1964, historically under its titular head, the Lord High Admiral – one of the Great Officers of State. For much of its history, from the early 18th century until its abolition, the role of the Lord High Admiral was almost invariably put "in commission" and exercised by the Lords Commissioner of the Admiralty, who sat on the governing Board of Admiralty, rather than by a single person. The Admiralty was replaced by the Admiralty Board in 1964, as part of the reforms that created the Ministry of Defence and its Navy Department (later Navy Command). Before the Acts of Union 1707, the Office of the Admiralty and Marine Affairs administered the Royal Navy of the Kingdom of England, which merged with the Royal Scots Navy and the absorbed the responsibilities of the Lord High Admiral of the Kingdom of Scotland with the unification of the Kingdom of Gr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Nautical Almanac
''The Nautical Almanac'' has been the familiar name for a series of official British almanacs published under various titles since the first issue of ''The Nautical Almanac and Astronomical Ephemeris'', for 1767: this was the first nautical almanac to contain data dedicated to the convenient determination of longitude at sea. It was originally published from the Royal Greenwich Observatory in England. 'ESAE 1961': Explanatory Supplement to the Astronomical Ephemeris and the American Ephemeris and Nautical Almanac' ('prepared jointly by the Nautical Almanac Offices of the United Kingdom and the United States of America', HMSO, London, 1961)'ESAA 1992': ed. P.K. Seidelmann, Explanatory Supplement to the Astronomical Almanac' (CA, 1992). A detailed account of how the publication was produced in its earliest years has been published by the National Maritime Museum. Since 1958 (with the issue for the year 1960), Her Majesty's Nautical Almanac Office and the US Naval Observator ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of UTC Time Offsets
This is a list of the UTC time offsets, showing the difference in hours and minutes from Coordinated Universal Time (UTC), from the westernmost (−12:00) to the easternmost (+14:00). It includes countries and regions that observe them during standard time or year-round. The main purpose of this page is to list the current standard time offsets of different countries, territories and regions. Information on daylight saving time or historical changes in offsets can be found in the individual offset articles (e.g. UTC+01:00) or the country-specific time articles (e.g. Time in Russia). Places that observe daylight saving time (DST) during their respective summer periods are listed only once, at the offset for their winter (usually known as "standard") period; see their individual articles for more information. A source for detailed DST and historical information is the tz database. Note that there are many instances of unofficial observation of a different offset (and/or DST) than ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Territorial Waters
The term territorial waters is sometimes used informally to refer to any area of water over which a sovereign state has jurisdiction, including internal waters, the territorial sea, the contiguous zone, the exclusive economic zone, and potentially the extended continental shelf. In a narrower sense, the term is used as a synonym for the territorial sea. Baseline Normally, the baseline from which the territorial sea is measured is the low-water line along the coast as marked on large-scale charts officially recognized by the coastal state. This is either the low-water mark closest to the shore, or alternatively it may be an unlimited distance from permanently exposed land, provided that some portion of elevations exposed at low tide but covered at high tide (like mud flats) is within of permanently exposed land. Straight baselines can alternatively be defined connecting fringing islands along a coast, across the mouths of rivers, or with certain restrictions across the mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
180th Meridian
The 180th meridian or antimeridian is the meridian 180° both east and west of the prime meridian in a geographical coordinate system. The longitude at this line can be given as either east or west. On Earth, these two meridians form a great circle that divides the earth into the Western and Eastern Hemispheres. The antimeridian mostly passes through the open waters of the Pacific Ocean, but also across land in Russia, Fiji, and Antarctica. An important function of this meridian is its use as the basis for the International Date Line, which snakes around national borders to maintain date consistency within the territories of Russia, the United States, Kiribati, Fiji and New Zealand. Starting at the North Pole of the Earth and heading south to the South Pole, the 180th meridian passes through: The meridian also passes between (but not particularly close to): *through the Aleutian Island chain of US territory *the Gilbert Islands and the Phoenix Islands of Kiriba ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gore (segment)
A gore is a sector of a curved surface or the curved surface that lies between two close lines of longitude on a globe and may be flattened to a plane surface with little distortion. The term has been extended to include similarly shaped pieces such as the panels of a hot-air balloon or parachute, or the triangular insert that allows extra movement in a garment (see Gore (fabrics)). Examples upleft, Red Hot air balloon * Globes of the Earth and the celestial sphere were first mass-produced by Johannes Schöner using a process of printing map details on 12 paper gores that were cut out then pasted to a sphere. This process is still often used. The gores are conveniently made to each have a width of 30 degrees of longitude matching the principal meridians from the South Pole and North Pole to the Equator. * Parachutes and hot air balloons are made from gores of lightweight material. The gores are cut from flat material and stitched together to create various shapes. * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
