The Greenwich Meridian, also known as the Prime Meridian, is an imaginary line of longitude that serves as the reference point for measuring longitude east and west of the Earth’s surface. It is defined as 0 degrees longitude and passes through the Royal Observatory in Greenwich, London, United Kingdom.
The establishment of the Greenwich Meridian as the Prime Meridian dates back to the late 19th century when it was internationally recognized as the reference point for standardizing timekeeping and navigation. This decision was made at the International Meridian Conference held in Washington, D.C., in 1884.
The adoption of the Greenwich Meridian as the Prime Meridian had several practical benefits:
1. **Standard Time**: It provided a common reference point for establishing time zones around the world. Time zones are typically measured in hours and minutes east or west of the Prime Meridian, with the time at the Prime Meridian itself being referred to as Greenwich Mean Time (GMT) or Coordinated Universal Time (UTC).
2. **Navigation**: The Prime Meridian serves as the starting point for measuring longitude, which is essential for navigation at sea and in the air. By knowing the difference in time between the local time and GMT, navigators can determine their position east or west of the Prime Meridian.
3. **Cartography**: The Prime Meridian is used as the central reference point for mapping the Earth’s surface in terms of longitude and for creating global coordinate systems used in cartography and geographic information systems (GIS).
The Greenwich Meridian has become a symbolic and historical landmark, attracting visitors to the Royal Observatory in Greenwich, where it is marked by a brass strip and a line on the ground. It remains the internationally recognized reference point for timekeeping and navigation, despite some countries using different reference points for their local timekeeping systems.