What is the prime meridian?

The prime meridian is indeed defined as the line of longitude at 0 degrees. It serves as the starting point for measuring longitude, which divides the Earth into the Eastern and Western Hemispheres. This line runs from the North Pole to the South Pole and provides a reference for timekeeping as well, establishing Greenwich Mean Time (GMT) based on its location passing through Greenwich, England. The prime meridian is fundamental to the geographic coordinate system used globally and plays a crucial role in navigation, mapping, and various scientific applications.