I have this "thought" experiment. Imagine a large rigid object, a thin disc (dime) with the ("heads") surface area of the earth, accelerating in the "heads" direction for many years such that individuals on the surface (of the "head" side) experience the normal sensation of "gravity". This object is the only object in the Universe. How long can the disc undergo this constant "felt" acceleration? (I believe the answer is "forever".) Does the force required to maintain the constant "felt" acceleration ever need to increase? (I believe the answer is "no".) Does the acceleration of the leading surface need to differ from the trailing surface in order for the disc to remain rigid at relativistic velocities? (I believe the answer is "yes".) Thanks so much!