What is the Greenwich Meridian?
The Greenwich meridian is the imaginary lineperpendicular to the equator, from which the earth’s length is measured and the time zone is established. It is also known as the base meridian, prime meridian or meridian 0.
As its name suggests, it runs through the Greenwich district of London. The Royal Greenwich Observatory is located there, the exact point of its trajectory.
Like any other meridian, the Greenwich meridian describes an imaginary line (semicircle) that goes from the North Pole to the South Pole, but it is from this specific meridian that it is establishes the division of the planet into two hemispheres (Western and Eastern) 180º each.
What is the Greenwich Meridian for?
The main functions of the Greenwich meridian are:
serve as a reference to know the earth’s longitude in degrees, that is, the distance of any place on the map with respect to this point; determine the time zone of each region of the globe.
Greenwich Meridian and the Equator
The Greenwich meridian and the perpendicular line of the equator establish the reference point from which the coordinate system of the globe.
If other meridians are established from the Greenwich meridian, the meridians are established from the equator line. parallels. Meridians and parallels measure longitude and latitude respectively, which is used to determine location on the map.
The Greenwich meridian line intersects perpendicularly with the equator line. The crossing point between both lines is called point 0and this is located in the waters of the Gulf of Guinea, west of Africa.
See also: Equator, Meridian, Latitude and Longitude.
Greenwich Meridian and time zone
To calculate the time of day in each region of the world (time zone), the Greenwich Meridian is taken as a reference. On each side of the Greenwich meridian, 12 meridians are drawn at a distance of 15º. This adds up to 24 meridians, corresponding to 24 hours of the day.
Each of the 12 lines east (right) of the Greenwich meridian adds up to one hour. Instead, each of the 12 lines to the west (left) subtracts one hour.
For example, if in London it is 00:00 hours (midnight), in Moscow it will be 03:00 am and in Mexico City it will be 06:00 pm the day before.
The account can be explained as follows: both hemispheres add up to 360º. When dividing 360 by 24, which is the number of hours in which the Earth rotates on its own axis (one day), the result is 15. Therefore, each meridian is located at a distance of 15º.
History of the Greenwich Meridian
It was in the 19th century when the urgent need to establish a main reference meridian and use the same name to call it became evident, so as to facilitate both navigation and trade, which had reached important levels of development.
For this purpose, the International Meridian Conference at the request of Chester A. Arthur, then president of the United States. The conference was held in the year 1884and would have the city of Washington as its headquarters.
Three proposals were presented to define the meridian 0:
The so-called “international” meridian, which crossed the province of Santa Cruz de Tenerife (El Hierro island); The meridian of the Paris Observatory; The meridian of the Royal Greenwich Observatory.
Of the 25 countries that attended, the votes were distributed as follows:
Votes in favor of the Greenwich Meridian: 22 (United States, Great Britain, Hawaii, Spain, Guatemala, Mexico, Colombia, Costa Rica, El Salvador, Venezuela, Paraguay, Chile, Italy, Netherlands, Switzerland, Sweden, Germany, Austria -Hungary, Russia, Liberia, Turkey and Japan); Votes against: 1 (Dominican Republic); Votes saved: 2 (France and Brazil).
See also: