Globes are maps represented on the surface of a sphere.
Great circle route, the shortest course between two points on the surface of a sphere.
In this case, space would be limited or bounded like the surface of a sphere.
The universe may be finite, though unbounded, like the surface of a sphere.
In a geometrical sense, curved surfaces, like the surface of a sphere, just don't lie flat — they don't have enough surface area.
For example, the surface of a sphere separates the interior from the exterior; a horizontal plane separates the half-plane above it from the half-plane below.
But how do you project an image so that it lands equally bright, focused and undistorted on the surface of a sphere?
The volume of a sphere is 4/3 π r^3 and the surface of a sphere is 4πr^2 (or 4 circular areas of πr^2).
Spherical trigonometry involves the study of spherical triangles, which are formed by the intersection of three great circle arcs on the surface of a sphere.
Consequently, the simplest descriptions of the star patterns and of the motions of heavenly bodies are those presented on the surface of a sphere.
C. 1 - 100 Menelaus of Alexandria, (flourished 1st century ad, Alexandria and Rome) Greek mathematician and astronomer who first conceived and defined a spherical triangle (a triangle formed by three arcs of great circles on the surface of a sphere).
