I am sure the rotating disc has been discussed on this forum over and over, but I could not find a thread. (Maybe I'm using the search function wrongly.) If someone could perhaps point me to a thread. I have read http://math.ucr.edu/home/baez/physics/Relativity/SR/rigid_disk.html This pdf is the best fairly balanced view I could find on the web. www.smcm.edu/nsm/physics/SMP03S/KeatingB.doc.pdf Any newer/better links?