I agree Martin, it's confusing :) Lightarrow sounds eminently reasonable to me. Murchie's idea make me think of gravitons and how they are thought to behave, getting all 'sticky' and clinging in a field created by our relative mass as we accelerate, and thereby build 'mass' and also slow time relative the original frame of reference and most parts of SpaceTime. And I agree that energy expended have to do with it, but in Lightarrow case it's a discussion of symmetry and the principle of equivalence, as I see it.

And in the end it seems to fall back to if you're ready to accept that distances actually contracts 'for real' when going closer to lights speed in a vacuum, or not. If you do then Lightarrow is your man :) If you don't? well? Then you will have to look at time dilation as being the 'real thing' here, and that should mean relative mass as Murchie describes it. For myself I think both are perfectly correct, and that we have both effects coordinating in that accelerating frame. Time dilation as well as Lorentz contraction.

When we talk about time dilation we will find it both in our accelerated frame (rocket), as well in a gravitational 'inertial' uniformly moving frame like earth. Even though the math seems to differ a little. I understand that 'gravitational time dilation' is equivalent to the 'velocity time dilation' at the escape velocity, which seems to mean that you by inserting the 'escape velocity' needed for your gravitational field (earth) in the SR formula (t=t*sqr(1-v^2/c^2) instead of 'v', you will get the equivalent time dilation, well as I understands it? So time dilation exist in all frames of invariant mass, as well as for relativistic, as well as momentum.