Final answer:
A great circle is a circle on the surface of a sphere that intersects with the plane passing through the center of the sphere, with Earth's equator being a prime example. Pilots and navigators in aviation are the occupations most interested in great circles for calculating the shortest and most efficient flight paths.
Step-by-step explanation:
A great circle is defined as a circle on the surface of a sphere, such as the Earth, that is the curve of intersection of the sphere with a plane passing through its center. This means that the center of a great circle is also the center of the sphere itself. An example of a great circle on Earth is the equator, which divides the Earth into the Northern and Southern Hemispheres. Lines of longitude or meridians also form great circles, which pass through the North and South Poles and are perpendicular to the equator.
An occupation most interested in understanding great circles is that of pilots and navigators, especially in the field of aviation. This is because the shortest path between any two points on the surface of the Earth is along the arc of a great circle. Understanding and utilizing great circles help these professionals to determine the most efficient flight paths, saving time and fuel.