I've just gotten around to reading "The Elegant Universe" and it has an explanation of why it is impossible to travel faster then light through the use of Einstein's equation E=mc^2 (pg 52). Greene says that the faster an object moves the more energy it has, and because of Einstein's equation the more energy something has the more mass it must have. My confusion here comes from having taken a basic modern physics course a couple months back where the total energy of a particle was determined by adding its Kinetic energy and the energy associated with its mass: 1/2mv^2 + mc^2. From the problems that my proffesor gave me it seemed that there was a seperation between the two. I understand that the higher an object's velocity the higher its Kinetic energy, but is this really interchangeble with its mass? What am I missing here?