Henry Segerman (Enneagonal hosohedron)

2-9-9 Topological Polyhedron, 3D-printed nylon.

[9 F, 9 E, 2 V]

This sculpture illustrates a subdivision of a sphere into nine bigons. A bigon is a polygon with only two sides. This is impossible for a polygon with straight sides living in the plane, but is no problem if we take a more topological version of a polygon.

With this broader interpretation of what a polyhedron is, we can think of this model as having two vertices, nine edges, and nine faces. Euler’s formula still applies here, since 2 – 9 + 9 = 2.