Some people know him as “the shape guy” or “mathematical Bob,” but no matter what you call Bob Sebrosky, the fact is the guy really loves his shapes. If you haven’t heard of him, maybe you’ve driven by his house on Rittenhouse Circle off Sardis Road North. The entire property is like a wonderland of tetrahedrons, bridges and walkways, cubes, octahedrons, helix staircases and icosahedrons, all handmade out of wood and ready to explore.
Sebrosky worked at IBM for 30 years and has always been somewhat of a handyman, but his fascination with shapes started when a neighbor suggested he make a rhombicosidodecahedron. For those who are not a geometry teacher or mathematician, a rhombicosidodecahedron is an Archimedean solid and one of 13 solids constructed of two or more types of regular polygon faces. It has 20 regular triangular, 30 square and 12 regular pentagon faces, as well as 60 vertices and 120 edges.
“I told him, ‘You’re nuts! You don’t even know what that is! I don’t even know what that is!” Sebrosky said.
Although Sebrosky’s neighbor was very intelligent, he lacked the skills to build the rhombicosidodecahedron himself. He begged Sebrosky to do it, and after a few weeks of trial and error, he finally did. He made the first model out of cardboard and then a wood version measuring 5 feet in diameter.
Sebrosky offered to donate the shape to the Town of Matthews so others could appreciate it, but town and park officials said the structure was too big and voiced concerns that children might play inside it and get injured. After a year and half, Sebrosky and the town eventually settled on a 30-inch model made of plastic-coated steel. It was installed in Squirrel Lake Park in June.
Since building his first rhombicosidodecahedron in 2000, Sebrosky has made more than 50 geometric shapes out of wood, both large and small. They are dispersed around his property, which he says has become somewhat of a photo-op for passersby and those who hear about it through word-of-mouth. Over the years, he said, students from nearby high schools and universities have reported on the shapes for class projects, and summer math camps have stopped by to ogle at the geometrical oddities.
“The first thing I say to people who stop by is, ‘Want to get inside a soccer ball?’” Sebrosky said, referring to the large, wooden truncated icosahedron in his backyard. “Kids climb inside and they just get a kick out of it.”
The rhombicosidodecahedron in Squirrel Lake Park is just a small part of Sebrosky’s larger dream to create a public “math” garden made up of geometrical shapes called polyhedrons. These include the five Platonic solids, prominent in the philosophy of Plato, and the 13 Archimedean solids, which take their name from Archimedes. He was a Greek mathematician, physicist, engineer, inventor and astronomer who discussed the shapes in his works.
Given the difficult approval process he endured with the rhombicosidodecahedron, Sebrosky knows an entire “math” garden with all 18 polyhedrons in Matthews might be a long shot. In the meantime, he’s hoping the town will allow him to donate another shape, specifically the truncated icosahedron, also known as a soccer ball. He’s currently working on a proposal.
“I’d like people to learn about the beauty of mathematics and geometry because geometry is really beautiful and artistic, too,” Sebrosky said.
Want to know more?
Information about the five Platonic solids and 13 Archimedean solids can be found on Bob Sebrosky’s website: www. polyhedrongarden.com.