We describe the 'Lie algebra of classical mechanics', modelled on the Lie algebra generated by kinetic and potential energy of a simple mechanical system with respect to the canonical Poisson bracket. It is a polynomially graded Lie algebra, a class we introduce. We describe these Lie algebras, give an algorithm to calculate the dimensions c n of the homogeneous subspaces of the Lie algebra of classical mechanics, and determine the value of its entropy lim n→∞ c