What are meridians of longitude?

Meridians of longitude are defined as great circles that pass through both poles and the center of the Earth. This characteristic is fundamental because it illustrates the way that longitude divides the globe into eastern and western hemispheres. Each meridian represents a line of constant longitude, and they are used to determine the geographic coordinates of a location—identifying how far east or west a point is from the Prime Meridian.

Understanding that meridians are great circles is crucial, as great circles represent the largest possible circle that can be drawn on a sphere, reflecting the shortest distance between two points on the surface of a globe. By intersecting at the poles, meridians indicate how longitude changes along the globe from 0° at the Prime Meridian to 180° in both directions.

The other options provide concepts that are important but do not accurately describe meridians of longitude. The mention of great circles connecting points of equal latitude pertains to lines of latitude (parallels), and small circles are not relevant in this context or related to longitude as they would represent circles that do not pass through the center of the Earth. Parallels are indeed used to define geographic coordinates, but they correspond to latitude, not longitude. Hence, the focus on meridi