Our planet is surrounded is by some imaginary lines to help us find an accurate position, distance, etc. These lines are known as Latitude and Longitude respectively. Latitudes are Horizontal imaginary lines. Whereas Longitudes are vertical lines. The prime meridian is the main longitude line passing through the middle of the Earth vertically. which is considered as the main reference for other longitudes. Read more on Geography topics here.

What is Prime Meridian?

Prime Meridian is the fictional line from the North Pole to the South Pole going through Greenwich in England and markings 0 ° longitude from where all other distances are measured. It is the 0 ° longitudinal line, the starting point for calculating distance across the Planet to both east and west. The prime meridian is subjective, which means it may be chosen anywhere.

Any longitude\inal line can act as the line of longitude with 0 degrees or main meridian. However, an international consensus is reached that the meridian passing through Greenwich, England, is called the main prime meridian. But not everyone or government accepts it as the main meridian. Any country could prepare maps, charts taking a longitudinal line passing through their capital cities or any other cities as the main meridian of 0 degrees longitude.

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What is Prime Meridian?

The Prime Meridian passes through Greenwich, UK

History of Longitude and the Prime Meridian

At first, the Greek Eratosthenes in Alexandria and Hipparchus in Rhodes established the concept of longitude. It was Ptolemy who first used a precise longitude in his Geographia for a world map. Around the 18th Century, people used different prime meridians for scientific purposes. Swedish people used meridian passing through Stockholm as the prime meridian. While french used longitudinal line passing through Paris as their Paris Meridian. But later around the end of the 19th century scientist realised having one fixed prime meridian will be a lot easier. Germany used the Berlin meridian, in Denmark the Copenhagen meridian was used, and in the UK they used Greenwich meridian.

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In 1884 a conference was held in Washington D.C. International Meridian Conference. Where 25 countries participated for a fixed meridian. Greenwich in the United Kingdom was chosen as the main meridian because two-third of the world ships at the time was using it as the main meridian. During voting 22 was in favor and 1 in against. San Domingo today’s Dominican Republic voted against the notion while Brazil and France abstained from the voting. Till 1911 France didn’t adapt to the Greenwich Meridian, they were using Paris as the main reference meridian.

Some Facts about the Prime Meridian

Here are some interesting facts about the main meridian:

  • It divides the world into the Eastern and Western Hemisphere.
  • For Earth and moon longitudes are measured from the main meridian (0°) to 180° in the East and 180° in the West.
  • And for all other celestial bodies longitude is measured from 0° to 360°.
  • It covers a distance of 20000 km from pole to pole.
  • Coordinated Universal Time (UTC) is based on the prime meridian.
  • It also helped to establish the International Dateline.
  • At 180° longitude is the international dateline.
  • It passes through the United Kingdom, France, Spain, Mali, Tongo, Ghana, Algeria, Faso, Burkina in the Northern Hemisphere.
  • In Southern Hemisphere, it only passes through Antarctica.
  • On the Sun are used two separate heliographic coordinate frameworks.
  • In 1975 Mercury’s prime meridian was identified as being 20 ° east of the Hun Kal crater.
  • The Moon’s prime meridian sits right in the center of the moon’s face observable from Earth and passes next to the Bruce crater.
  • In 1992 the primary meridian of Venus passing through the central peak of the Ariadne crater was identified.
  • Mars’ main meridian was identified in 1971 which passes through the Airy-0 crater center.
  • Pluto’s prime meridian was identified as the face of the planet which faces directly to its largest moon Charon.