Scattering by the sphere

Next year brings the 100th anniversary of Watson's classic paper "The diffraction of electric waves by the earth" and I would like to use this as a welcome excuse to review various results about scattering by spherical obstacles.  Is the sphere determined by its scattering resonances among other obstacles?  Do waves decay faster or slower for other obstacles of the same diameter?  What about resonances of hollow spheres, that is, of Helmholtz resonators?  What about spheres in hyperbolic space?  Some of the talk is based on recent work with Peter Hintz.