Can the ehrenfest paradox be resolved using STR or does one require to go in general theory? If it can be, please recommend a book or online source which explains it from the basics. Also I'm somewhat unclear on what exactly the paradox is,does it state that- Since the ratio of it's circumference and diameter is less than π it follows non euclidian geometry. So what if it is a non euclidian geometry? How can that statement be a paradox?