 It is so called because such an embedding can be found as the equilibrium position for a system of springs representing the edges of the graph.Steinitz's theorem states that every 3-connected planar graph can be represented as the edges of a convex polyhedron in three-dimensional space.A straight-line embedding of formula_1 of the type described by Tutte's theorem, may be formed by projecting such a polyhedral representation onto the plane.