Basic question I'm sure but...please help... If there is an object of some mass accelerating toward some other massive object, I can see that total energy of system is same regardless of time as potential energy from gravity well is being lost as kinetic energy of object increases. It would appear that total energy in system is unchanged. 1) Am I correct in this understanding ? 2) If the object in question was say moving at the speed of light to start with, as the object gets closer to other massive object, isn't the gravity potential still being reduced over time ? 3) But object cannot gain any more kinetic energy (already at top speed) so I am thinking the total energy of this system is reducing as object gets closer to massive object ? But this cannot be the case... I know I am missing a piece of the equation here, what is happening in this situation ?