What defines a Great Circle?

A Great Circle is defined as the intersection of a sphere and a plane that passes through the center of the sphere. This geometric definition is fundamental in navigation and geography because Great Circles represent the shortest distance between two points on the surface of the sphere, which is the Earth in this context.

When navigating, especially over long distances, using Great Circles is crucial for efficiency and accuracy. This concept is utilized in aviation and maritime navigation to plot the most efficient routes.

The other options do not accurately describe a Great Circle. While the path between two cities might be a Great Circle route, it does not define what a Great Circle is. Similarly, a line connecting all points of equal latitude describes a parallel or latitude line, but not a Great Circle, which may cross different latitudes. Lastly, a visual representation of the Earth's surface does not encompass the mathematical and geometric definition of a Great Circle itself.