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The Greenwich meridian is a prime meridian, a geographical reference line that passes through the Royal Observatory, Greenwich, in London, England. [1] From 1884 to 1974, the Greenwich meridian was the international standard prime meridian, used worldwide for timekeeping and navigation. The modern standard, the IERS Reference Meridian, is based ...
A prime meridian is an arbitrarily chosen meridian (a line of longitude) in a geographic coordinate system at which longitude is defined to be 0°. Together, a prime meridian and its anti-meridian (the 180th meridian in a 360°-system) form a great circle. This great circle divides a spheroid, like Earth, into two hemispheres: the Eastern ...
The Prime Meridian of these modern reference systems is the IERS Reference Meridian, in full the International Earth Rotation and Reference Systems Service Reference Meridian (in short called the IRM), which is 102.5 metres east of the Airy Greenwich astronomical meridian represented by the stainless steel strip, which is now 5.31 arcseconds west.
The International Date Line (IDL) is the line between the South and North Poles that is the boundary between one calendar day and the next. It passes through the Pacific Ocean, roughly following the 180.0° line of longitude and deviating to pass around some territories and island groups. Crossing the date line eastbound decreases the date by ...
Greenwich Mean Time is defined in law as standard time in the following countries and areas, which also advance their clocks one hour (GMT+1) in summer. United Kingdom, where the summer time is called British Summer Time (BST) Ireland, where it is called Winter Time, [22] changing to Standard Time in summer. [21]
The International Meridian Conference was a conference held in October 1884 in Washington, D.C., in the United States, to determine a prime meridian for international use. [1] The conference was held at the request of U.S. President Chester A. Arthur. [1] The subject to discuss was the choice of "a meridian to be employed as a common zero of ...
Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communication, navigation, scientific research, and commerce. UTC has been widely embraced by most countries and ...
First point of Aries. The first point of Aries defines the ecliptic coordinate of (0°, 0°). It is on the celestial equator at both the left and right extremes of the sky chart, with the ecliptic (the orange dotted sine curve) passing through it. The first point of Aries, also known as the cusp of Aries, is the location of the March equinox ...