Bezdek's Unistable Polyhedron With 18 Faces
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This Demonstration shows Bezdek's unistable polyhedron with 18 faces. A face is stable if, and only if, the orthogonal projection (red point) of the center of mass (black point) onto the face lies inside the face. A unistable polyhedron has only one stable face. The polyhedron is a skew pyramid placed along the axis and can be changed using the sliders.
Contributed by: Izidor Hafner (December 2015)
Open content licensed under CC BY-NC-SA
Guy constructed unistable 19-faces solid in 1968 [2, 3, 4]. Bezdek found unistable 18-faces solid in 2011 . In  Reshetov constructed unistable polyhedra with 14, 15, 16, and 17 faces.
 A. Bezdek, On stability of polyhedra, Workshop on Discrete Geometry, 13-16 September 2011, Fields Institute, Canada (2011), pp. 2490-2491.
 J. Bryant and C. Sangwin, How Round Is Your Circle?: Where Engineering and Mathematics Meet, Princeton: Princeton University Press, 2008 pp. 273–276.
 R. K. Guy, A Unistable Polyhedron, Calgary: University of Calgary Department of Mathematics, 1968.
 J. H. Conway, M. Goldberg, and R. K. Guy, Problem 66-12, SIAM Review 11, 1969 pp. 78–82.
 A. Reshetov, A Unistable Polyhedron with 14 Faces, International Journal of Computational Geometry & Applications, Vol. 24, No. 1 (2014) pp. 39-59.
"Bezdek's Unistable Polyhedron With 18 Faces"
Wolfram Demonstrations Project
Published: December 9 2015