The Greenwich Meridian, also known as the Prime Meridian, is the line of longitude defined to be 0 degrees. It runs from the North Pole to the South Pole and passes through Greenwich, a district in London, England. This meridian serves as the starting point for measuring longitude and is used to establish time zones around the world. Established in 1884 during the International Meridian Conference, the Greenwich Meridian was chosen to standardize timekeeping and navigation. It divides the Earth into the Eastern and Western Hemispheres, making it a crucial reference point for geography, cartography, and global positioning systems.