Truncated icosahedron

Intuitively, it may be regarded as footballs (or soccer balls) that are typically patterned with white hexagons and black pentagons.

Each of the 12 vertices at the one-third mark of each edge creates 12 pentagonal faces and transforms the original 20 triangle faces into regular hexagons.

[1] Therefore, the resulting polyhedron has 32 faces, 90 edges, and 60 vertices.

[2] A Goldberg polyhedron is one whose faces are 12 pentagons and some multiple of 10 hexagons.

describes how closely a polyhedron resembles a sphere.

[4] The truncated icosahedron is an Archimedean solid, meaning it is a highly symmetric and semi-regular polyhedron, and two or more different regular polygonal faces meet in a vertex.

[9] According to Steinitz's theorem, the skeleton of a truncated icosahedron, like that of any convex polyhedron, can be represented as a polyhedral graph, meaning a planar graph (one that can be drawn without crossing edges) and 3-vertex-connected graph (remaining connected whenever two of its vertices are removed).

It is a cubic graph, meaning that each vertex is incident to exactly three edges.

[11][12][13] The balls used in association football and team handball are perhaps the best-known example of a spherical polyhedron analog to the truncated icosahedron, found in everyday life.

[16] Geodesic domes are typically based on triangular facetings of this geometry with example structures found across the world, popularized by Buckminster Fuller.

An example can be found in the model of a buckminsterfullerene, a truncated icosahedron-shaped geodesic dome allotrope of elemental carbon discovered in 1985.

[17] In other engineering and science applications, its shape was also the configuration of the lenses used for focusing the explosive shock waves of the detonators in both the gadget and Fat Man atomic bombs.

[13] The truncated icosahedron was known to Archimedes, who classified the 13 Archimedean solids in a lost work.

All that is now known of his work on these shapes comes from Pappus of Alexandria, who merely lists the numbers of faces for each: 12 pentagons and 20 hexagons, in the case of the truncated icosahedron.

The first known image and complete description of a truncated icosahedron are from a rediscovery by Piero della Francesca, in his 15th-century book De quinque corporibus regularibus, which included five of the Archimedean solids (the five truncations of the regular polyhedra).

[19] The same shape was depicted by Leonardo da Vinci, in his illustrations for Luca Pacioli's plagiarism of della Francesca's book in 1509.

Although Albrecht Dürer omitted this shape from the other Archimedean solids listed in his 1525 book on polyhedra, Underweysung der Messung, a description of it was found in his posthumous papers, published in 1538.

Johannes Kepler later rediscovered the complete list of the 13 Archimedean solids, including the truncated icosahedron, and included them in his 1609 book, Harmonices Mundi.

3D model of a truncated icosahedron
The truncated icosahedral graph
The truncated icosahedron (left) compared with an association football
Piero della Francesca 's image of a truncated icosahedron from his book De quinque corporibus regularibus