very nice problem
Source: meditranean 2003
March 16, 2009
geometry3D geometryspherecombinatorics unsolvedcombinatorics
Problem Statement
Consider a system of infinitely many spheres made of metal, with centers at points . We say that the system is stable if the temperature of each sphere equals the average temperature of the six closest spheres. Assuming that all spheres in a stable system have temperatures between and , prove that all the spheres have the same temperature.