Prime Meridian is the meridian at 0° longitude passing through the Royal Observatory in Greenwich.
Prime Meridian and its anti-meridian form an imaginary orthodrome or the great circle. This circle divides the spheroid of Earth into two equal halves, namely Eastern Hemisphere and Western Hemisphere.
History of Prime Meridian
In third century BC, Eratosthenes proposed a system of latitude and longitude for the first time. This was a significant development as it made cartography and navigation more precise. Nevertheless, it was Claudius Ptolemy who used the first consistent meridian in the map of the world in his book Geographia. This book was based on the contemporary geographical knowledge available during the second century Roman Empire.
Unlike the Equator, which is naturally determined by the axis of Earth’s rotation, there exists no natural basis of Prime Meridian. Hence, in 18th century, many countries had adopted their own Prime Meridian but need for a common Prime Meridian for the world was always felt.
Why Greenwich is the Prime Meridian?
Sir George Airy established Greenwich Meridian in 1851. An International Meridian Conference was held at the request of the 21st President of the United States Chester Alan Arthur in the year 1884 in Washington D.C. At the conference 22 countries voted to adopt Greenwich as the prime meridian of the world.
The primary reasons attributed for having worked in favour of Greenwich were:
- The United States, which was a powerful nation back then, had already adopted Greenwich Meridian as the Prime Meridian and adjusted their national time zone system accordingly.
- Majority of the world’s navigation was dependent on the sea charts which referred to Greenwich as the Prime Meridian.
- The anti-meridian of Greenwich, where the date changes, should be such that it passes through the least amount of land area in order to avoid date change-related confusion in areas.