I'll start with link describing the phenomenon: https://books.google.com/books?id=W...&q=relativity twist rotating cylinder&f=false Quote: "A cylinder rotating uniformly about the x' axis in the frame S' will seem twisted when observed in the usual second frame S, in which it not only rotates but also travels forward." Now picture that instead of a cylinder we have a helix in S'. The helix in S' has an integer number of curls in S', so its center of gravity is on the x' axis. It rotates independently in S'. If its pitch in S' is such that the twisting seen in S perfectly straightens it out then an observer in S sees a rod that is not on the x axis rotating around the x axis all by itself. How can that be? Or, where have I gone wrong?