For a magnetic dipole of fixed orientation (and constant magnitude) the energy will be given by U = − − M ⋅ ⋅ B = − − ( M x B x + M y B y + M z B z ) , where M x, M y and M z are constant. In this case the Laplacian of the energy is always zero, ∇ ∇ 2 U = 0 , so the dipole can have neither an energy minimum nor an energy maximum. That is, there is no point in free space where the dipole is either stable in all directions or unstable in all directions.