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 f unctions can be derived and visualized using this path, known as Seiffert's spiral. (C) 2000 American Association of Physics Teachers.