[Spaceships] Real Life Non-Super Science Reactionless Engines

[Agemegos]

Originally Posted by malloyd

Of course you can. You can select a preferred frame in which the physics are defined. That works fine, but you have to abandon the notion there is nothing but coincidence that's special about that frame.

Agreed. I'm just saying that if you do (abandon the Postulate of Relativity) you can end up with a case in which travel occurs along a space-like interval (FTL in some inertial frames of reference, backward-in-time in others, instantaneous in boundary cases) but it is not possible for any signal from the arrival event to get back within the past-ward light-cone of the departure event.