Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is measured in degrees, with the prime meridian at Greenwich, England serving as the starting point at 0 degrees. As you move east or west from this line, the degrees increase up to 180 degrees. Longitude helps us determine how far a location is from the prime meridian, which is essential for navigation and mapping. Understanding longitude is crucial for various activities, including global positioning systems (GPS) and cartography. By combining longitude with latitude, which measures north-south positions, we can pinpoint exact locations on the globe. This system allows travelers, scientists, and explorers to communicate and navigate effectively across vast distances.