Why can’t an object with non-zero rest mass be accelerated to travel faster than the speed of light?
Another consequence of Einstein’s postulates is that it is not possible to accelerate an object with non-zero rest mass to a speed greater than the speed of light. Conversely, every object with zero rest mass – such as a photon – is always travelling at the speed of light. Students should understand that if we apply a force to accelerate an object the energy we provide is transformed into the kinetic energy of the object. The kinetic energy of an object is given by Ek = (γ-1)m0c2, where as v approaches c, γ approaches infinity. So we would have to provide an infinite amount of energy to accelerate an object to the speed of light.
