But the earth is a three-dimensional sphere.

In his hypothetical world of two-dimensional triangles and squares, a three-dimensional sphere was an incomprehensible object.

A more easily visualized "projection" is that of a three-dimensional sphere.

Take a copy of S, the three-dimensional sphere.

It says, essentially, that the three-dimensional sphere is the only bounded three-dimensional space with no holes.

A map projection is a way of showing the surface of a three-dimensional sphere on a plane.

He is then visited by a three-dimensional sphere, which he cannot comprehend until he sees Spaceland for himself.

These maps are three-dimensional spheres of twine and sticks.

Go up another dimension, and any four points in space can be located on the curved sur-face of a three-dimensional sphere.

When a three-dimensional sphere is projected onto a plane, its projection will either be a circle or an ellipse.