Well if we consider that "something" can be really "mass less" , would it be correct to consider it to move at the speed of light? If yes, then I have a little doubt. Let's say it moves at the speed of light , then if we apply the mass equation (mass=[(rest mass)/squared root(1-(v^2)/(c^2))] , then we should end up at an indeterminate form , saying that the mass of that "mass less" body is indeterminate when in motion. Are we right to say this? How can mass be indeterminate ? If no, then what perhaps that "mass less" body would be doing around?