This story is a supplement to the feature "Using Causality to Solve the Puzzle of Quantum Spacetime" which was printed in the July 2008 issue of Scientific American.

A Mosaic of Triangles
To determine how space sculpts itself, physicists first need a way to describe its shape. They do so using triangles and their higher-dimensional analogues, a mosaic of which can readily approximate a curved shape. The curvature at a point is reflected in the total angle subtended by the triangles that surround it. For a flat surface, the angle is exactly 360 degrees, but for curved surfaces it can be less or more.