Akin to the distinction between quantum and classical mechanics, Albert Einstein 's general and special theories of relativity have expanded the scope of Newton and Galileo 's formulation of mechanics. The differences between relativistic and Newtonian mechanics become significant and even dominant as the velocity of a body approaches the speed of light. For instance, in Newtonian mechanics, the kinetic energy of a free particle is E = ⁠ 1 / 2 ⁠ mv, whereas in relativistic mechanics, it is E = (γ − 1) mc (where γ is the Lorentz factor ; this formula reduces to the Newtonian expression in the low energy limit).