# Definition:Great Circle

## Definition

Let $S$ be a sphere.

A great circle of $S$ is defined as the intersection of $S$ with a plane passing through the center of $S$.

### Pole of Great Circle

Let $C$ be a great circle of $S$.

Let $AB$ be the diameter of $S$ situated perpendicular to the plane of $C$.

The points $A$ and $B$, where the diameter intersects $S$, are the poles of the great circle $C$.

### Axis of Great Circle

The axis of a great circle $C$ is the straight line that joins the poles of $C$.

## Examples

### Earth's Surface

A great circle between two locations $A$ and $B$ on the surface of Earth can be used as the shortest distance to travel from $A$ to $B$.

## Also see

• Results about great circles can be found here.