According to the Gauss-Bonnet Theorem, the total curvature of a smooth convex surface is 4. We can check that this statement holds for the more exotic curvature of the Sphericon.

The Sphericon has four cone-points and two arcs of zip-loci.Otherwise it has no curvature, since it can be assembled fromflat pieces without stretching.

- At each cone-point there is a concentration of curvatureequal to -. Total contribution from cone-points:4 - 4.
- If the common radius of the cones is R, then each componentof the zip-locus has length R. Since a length L of zip-locuscarries a concentration 2L/R of curvature, each component of thezip-locus contributes 2L/R x R = 2 of curvature. Totalcurvature carried by the zip-locus: 4.
- Total curvature of the Sphericon: 4.

On to Sphericon page 7.

Back to Sphericon page 5.