The prime meridian is an imaginary line that runs from the North Pole to the South Pole, dividing the Earth into the Eastern and Western Hemispheres. It is located at 0 degrees longitude and serves as the starting point for measuring longitude. The prime meridian passes through the Royal Observatory in Greenwich, England, which is why it is often referred to as the Greenwich Meridian. Established in 1884, the prime meridian is crucial for navigation and mapping. It helps in determining time zones, with each zone typically spanning 15 degrees of longitude. This system allows for a standardized way to coordinate time across the globe, making it easier for travel and communication.