A neon-framed model of a regular tetrahedron hangs in an entrance to the Milan Central Train Station (Stazione di Milano Centrale).
Defined by four triangular faces, the tetrahedron is the simplest of all polyhedra. Any four points in space that are not in the same plane mark its corners.
Despite its apparent simplicity, a variety of artists have used the tetrahedron as the inspiration for artworks (see, for example, "Three Sentinels"). Part of the visual appeal of these constructions is that a tetrahedron is so angular that its aspect can change abruptly as a viewer moves around to see it from different angles.
One enthusiast of the tetrahedron was Philadelphia-based artist Robinson Fredenthal (1940-2009). His large, angular sculptures take advantage of the tetrahedron's amazing rigidity and its ability to resist an incredible amount of force from the outside.
"I can't think of anything more perfect than a tetrahedron," Fredenthal once remarked. If visitors came from outer space, "I'd hand them a tetrahedron, and they would understand."
Fredenthal manipulated tetrahedra in a variety of ways, creating peculiarly balanced, leaning towers of tetrahedra, and great bridges of these remarkable forms.
Fredenthal's Black Forest (above) is located on the campus of the University of Pennsylvania.
A bridge of tetrahedra forms the basis for Fredenthal's sculpture White Water, found at 5th and Market Streets in Philadelphia.
Huge tetrahedra representing Fire Water Ice loom tall in a three-part sculpture at 1234 Market Street in Philadelphia.
Afflicted with Parkinson's disease for much of his life, Fredenthal spent his time in geometric exploration, crafting thousands of small-scale cardboard models of variations of simple forms such as cubes and tetrahedra. Most of his models are now in the Penn architectural archives.
Peterson, I. 2001. Fragments of Infinity: A Kaleidoscope of Math and Art. Wiley.
Photos by I. Peterson