Meaning of Greenwich Meridian
What is Greenwich Meridian:
Greenwich Meridian is the name used to designate the base meridian, prime meridian or meridian 0, from which the land longitude is measured and the time zone is established. It receives this name for crossing the Greenwich district of London. There is the Royal Greenwich Observatory, 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 the division of the planet into two hemispheres of 180º each is established: the western hemisphere and the eastern hemisphere.
The main functions of the Greenwich meridian are:
- serve as a reference to know the terrestrial longitude in degrees, that is, the distance of any place on the map with respect to this point;
- determine the time zone for each region of the globe.
Greenwich Meridian and the Equator
The Greenwich meridian and the perpendicular line of the equator are the reference point from which the coordinate system of the globe is established.
If other meridians are established from the Greenwich meridian, the parallels are established from the equator. 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 the two lines is called point 0, and this is in the waters of the Gulf of Guinea, west of Africa.
Greenwich Mean Time and Time Zone
To calculate the time of day in each region of the world, the Greenwich meridian is taken as a reference. On each side of the Greenwich meridian, 12 meridians are plotted at a distance of 15º. This adds up to 24 meridians, corresponding to 24 hours a day.
Each of the 12 lines east (right) of the Greenwich Mean Time 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 a.m. and in Mexico City it will be 06:00 p.m. the previous day.
The count 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.