http://en.wikipedia.org/wiki/Bell's_spaceship_paradox#Importance_of_length_contraction In Bell's spaceship paradox, the spaceships appear to maintain distance from one another from inertial frame S. Got it. But because of length contraction within each rigid body, when observed from the frame of one space ship, the distance between the ships would expand and the "contraction" isn't seen. Got it. How, though, is this due to unequal accelerations as claimed by apparently every great name attached to this? I see that from the perspective of one spaceship, the other ship will appear to accelerate away. But why? Where does this derive from? I'm failing to attain a visceral understanding of where the difference in velocity is arising. Bonus question: If this kind of expansion between bodies requires the frame to be moving relative to an inertial frame, is this effect inherently reliant on an inertial frame existing? See, from the perspective of the ships, they may see one another accelerate away inexplicably if the inertial frame is sufficiently unapparent. Forgive me, but this reminds me quite a bit of dark energy/cosmic expansion. Thanks to anyone with the patience to walk me through this.