On traveling round without feeling it and uncurving curves, M.A. Abramowicz and J.P. Lasota, Am. J. Phys. 54(10), October 1986
We discuss elementary example of how, in a strong gravitational field, the basics kinematical concepts of acceleration and circular motion seem to have paradoxical properties. This allows insight into the physical significance of space-time curvature without the use if difficult mathematical formalism