was the host of the International Meridian Conference whose aim was to establish a standard prime meridian to unify the local times used in railway timetables. Along its stretch, the Greenwich Prime Meridian passes through nine countries which are Spain, UK, France, Mali, Togo, Burkina Faso, Algeria, Ghana, and Queen Maud Land, a Norwegian territory in Antarctica. The Greenwich Prime Meridian starts from the North Pole in the Arctic Ocean and runs southwards to the South Pole in Antarctica. It was established so that it lies 5.3 seconds to the west of the actual 0-degree, 0-minute, and 0-second longitude. The Greenwich Prime Meridian was used as the universal base point in the calculation of longitude until the IERS Reference Meridian was established in 1983 through the Global Positioning System (GPS) showed that the Greenwich Meridian was not precisely located along the 0-degree, 0-minute and 0-second longitude. The Greenwich Prime Meridian was adopted as the universal prime meridian after leaders and scientists from all over the world met for the International Meridian Conference in 1884 which was took place in Washington D.C., USA. Increased globalization experienced in the early 20th century attributed to the improved sea and air travel made it necessary for the countries around the world to have a common prime meridian which could be used as the universal reference point for longitude to be used for trans-continental and trans-oceanic travel by ship and airplane captains. In several instances, the Greenwich meridian was moved few meters eastwards as improvements in technology allowed the use of better instruments. One of such countries was Great Britain which established its distinct meridian which passed through the Royal Observatory situated at Greenwich.

Before it was mapped as Greenwich Prime Meridians, countries all over the world used their prime meridian which passed through their respective boundaries and usually cut across such nation’s capital city. The Greenwich Meridian was established in 1851 by 19th-century British mathematician and astronomer, Sir Biddell Airy. The Greenwich Prime Meridian was established at Royal Observatory in London and it is the universal prime meridian. Prime meridians are established on most of the major celestial bodies of the Solar System including the planets as well as some large moons. Any prime meridian is geographically and mathematically defined and is located at the 0-degree longitude and therefore is used as the base point for other longitudes which are measured in the degrees to the west or east of the prime meridian they are located. A prime meridian is a geographic longitude which runs vertically along a sphere dividing it into two hemispheres.

The Change by C.M. Meridian