Assume a 200 ft diameter by 500 ft long spaceship traveling just under the speed of light, like .99999c.
To an outside observer, does the ship really appear to be only a little over 2 feet long? Like, instead of a beer can shape, it would be basically a flat disc 200 ft in diameter? Assuming a vantage point far enough away to be able to see it pass, and assuming a telescope with some sort of compensation for the blue and red shift as it approached and passed, would you actually see relativistic compression?
Second, what would happen if the ship hit a star at that speed (or faster)? Would the ship’s momentum and “relativistic mass” protect it and let it pass through unscathed, like a knife through butter? From the ship’s POV it would take about 4 seconds to pass through (if it survived). Or would it be the biggest firework anyone has ever seen? Either way, would the star survive? Would it make a difference if the ship didn’t go through the star’s core?