Spiraling the Earth with C. G. J.!Jacobi

The simple requirement that one should move on the surface of a sphere with constant speed while maintaining a constant angular velocity with respect to a fixed diameter, leads to a path whose cylindrical coordinates turn out to be given by the Jacobian elliptic functions. Many properties of these functions can be derived and visualized using this path, known as Seiffert's spiral. (C) 2000 American Association of Physics Teachers.