Please refer to http://en.wikipedia.org/wiki/Ehrenfest_paradox for a description of this very interesting paradox. Although I understood the apparent paradox, I could not get a grasp of the resolution ofthe paradox, as explained on Wikipedia. Could any of the pros on this forum explain the resolution in more simple terms? I still could not understand how an observer at rest will be able to reconcile the fact that she is observerving a circumference less than 2pi times the radius that she observes. No shape in Euclidean geometery would satisfy what she observes. And how could the space between the axis of rotation of the train and the circular path become bent simply due to the motion of the train? More puzzling is the view from the perspective of an observer on the rim of the disc. She actually measures a circumference greater then 2pi.