Suppose, there are two inertial frame first is in motion with constant speed and second is motionless. We can say that two frames are relatively in motion with each other with constant speed. So time would slowdown for each frame referenced by other frame. But after some long journey first frame feels some force and start coming back, after long journey first frame is now standing near second frame with less aged. Time slowdown for both frames but it is maintained only for first frame. why..? What do the force render its roll in the scenario...? Why the Length Contraction cannot be maintained..?