Consider a particle of mass m orbiting a much heavier object of mass M. Assume Newtonian mechanics, which is both classical and non-relativistic. The conservation of energy and angular momentum give two constants E and L, which have values E = 1 2 m ( r ˙ ˙ 2 + r 2 ϕ ϕ ˙ ˙ 2 ) − − G m M r , L = m r 2 ϕ ϕ ˙ ˙ when the motion of the larger mass is negligible. In these expressions,