If a spaceship has enough power sometime in the future to achieve an appreciable fraction of the speed of light, what exactly will be compressed along the direction of its travel, relative to our slower frame of reference? Are the atoms (or the particles making up the atoms) which make up the spaceship themselves distorted, or only the space between them, or both, or neither? Or only the macro form of the ship disregarding the atoms? Or what? Another way of asking this is what exactly is distorted in a proton going at almost light speed in a supercollider. We know the proton gets more massive, relative to us. Is it actually compressed or shortened along the axis of its line of travel?