Hello folks! I have just come from a night at the pub with fellow students of life where over many a pint several mysteries of the universe were discussed. One of my friends asked me a question concerning special relativity that initially took me by surprise and which has me wondering about the nature of energy in relativity theory. The question was this: How is it that something can be said to have kinetic energy when, in its own reference frame, it has zero velocity? If it too is relative, what are the implications of that? Initially I didn't have a good response, because I'd never given it any thought, but after a length of time I cobbled together what I think the answer is, but I would love to hear what the answer actually is if it's out there somewhere. My answer is something like this: Kinetic energy is not relative! It is the work done in accelerating an object from 0 m/s up to its final velocity. Even though a moving object has zero velocity in its inertial reference frame, it needed to accelerate to get there, and this was done with respect to absolute space-time. Or something like that. My mind is a bit boggled at the moment, but I feel like this answer doesn't quite tell the whole story. So what is the actual state of affairs?