What do meridians, or lines of longitude, measure?

Meridians, or lines of longitude, are specifically designed to measure the arc distance east and west of the prime meridian. The prime meridian, which is established at 0 degrees longitude, serves as the reference point from which all other longitudes are calculated. Each meridian extends from the North Pole to the South Pole, representing degrees of longitude that indicate how far, in terms of angular distance, a location is positioned either east or west of this reference line.

The concept of longitude allows humans to pinpoint locations on the Earth’s surface and is crucial for navigation, cartography, and understanding geographic information. While other options refer to latitude or different measurements, they do not correctly represent the function of meridians in measuring east-west positions.