1. The problem statement, all variables and given/known data The given problem is that we have a rocket ship, accelerating at a constant rate of 1g (in its own instantaneous inertial rest frame) for 40 years. We must find the distance it travels in that time, as measured by an observer on earth. 2. Relevant equations dx'=gamma*(dx-vdt) dt'=gamma*(dt-vdx/c^2) 3. The attempt at a solution I have derived the relationship a'=a/(gamma^3*(1-uv/c^2)^3) Given that the rocket has constant acceleration in its own rest frame, a'=g Given that the observer on earth is stationary, u=0 If we use these two facts, we get that g*gamma^3=a, which is nonsensical because that means that at very high velocities, the observed acceleration is higher than g when it should be lower. Where is my error?