The prime meridian is the zero-degree of longitude, where the East meets the West. It is an arbitrary line, meaning any line of longitude could be chosen as the prime meridian. However, the international agreement of ‘International Meridian Conference,’ agreed upon the meridian running through Greenwich as the official prime meridian of the world. Also called the Greenwich meridian, it separates the Eastern hemisphere from the Western hemisphere, as similar to the Equator dividing the Northern and the Southern hemispheres. Terminating at the North and South poles, the imaginary line of prime meridian and its counter meridian: the 180th meridian form a Great circle.
Prior to the establishment of a universal prime meridian, each nation took the freedom to decide their own meridians, usually passing through their respective countries. But this was inconvenient for the sailors and the travelers of the 19th century, to refer on their maps for trans-continental and trans-oceanic travels. Hence, there arrived a need to establish a globally accepted prime meridian. In the International Meridian Conference, held in Washington, D.C., in 1884, a group of forty-one delegates from twenty-five nations gathered and chose the meridian passing through the Airy transit circle telescope, housed at the Royal Observatory, Greenwich, London as the prime meridian. The two primary reasons the that the Greenwich meridian was chosen as the prime meridian were: its already being referred by over two-thirds of the world’s ships in their maps and charts, and 72% of the world’s commerce depended on sea-charts that used Greenwich as Prime Meridian.
The Greenwich meridian is also used as the reference for all other meridians of longitude, numbered with East or West of it. Serving as the basis of the world’s Standard Time Zone system, the mean Solar Time at Greenwich is accepted as the Universal Time. Formerly called the Greenwich Mean Time, the standard time subsequently becomes, 4 minutes earlier at each longitude West of the Greenwich and four minutes later at each longitude East of the Greenwich. This acceptance of Greenwich Meridian as the universal base point in the calculation of longitude, was altered after the IERS Reference Meridian was established in 1983 through the Global Positioning System (GPS). The findings revealed that the Greenwich meridian does not fall precisely on the zero-degree, zero-minute and zero-second longitude. But it lies 5.3 seconds West to the actual zero-degree longitude.
Featuring a total length of 12,429.9 miles, the Greenwich meridian, is of the same length as any other meridian of longitude. In the Northern hemisphere, it passes through the United Kingdom, France, Spain, Algeria, Mali, Burkina Faso, Togo and Ghana. Whereas the only landmass in the Southern hemisphere, through which the Greenwich passes, is the Queen Maud Land in Antarctica.
The meridian’s fame has hundreds of visitors from all over the world, making their way to the Royal Observatory. The prime meridian was long symbolized by a brass strip in the courtyard which was later replaced by stainless steel in 1999. It has been marked by a powerful green laser shining across the London night sky.
The underlying table mentions the countries that lie on the Greenwich meridian:
|Countries on the prime meridian|
|Queen Maud Land in Antarctica (Region of Antarctica)|