What is the Prime Meridian?
The Prime Meridian is the line of 0 degrees longitude, running from the North Pole to the South Pole through Greenwich in London. It divides the Eastern and Western Hemispheres.
Lines of longitude, called meridians, measure distances east and west. Any meridian could have been chosen as zero. At the International Meridian Conference in Washington, D.C., in 1884, most countries agreed to use the meridian passing through the Royal Observatory in Greenwich.
Greenwich was chosen partly because many ships already used British charts based on it. The Prime Meridian also became the basis of Greenwich Mean Time, the reference point for world time zones, later replaced in science by Coordinated Universal Time.
Countries on the line
The Prime Meridian passes through the United Kingdom, France, Spain, Algeria, Mali, Burkina Faso, Togo and Ghana, as well as Antarctica. On the opposite side of the world, at 180 degrees, lies the International Date Line.
Did You Know?
The line marked at the Royal Observatory is not quite where GPS puts 0 degrees. Because of differences in how the Earth's shape is measured, the GPS zero line lies about 100 meters to the east.