  We compute the exterior Green function for a grounded equi-potential circular
ring in two-dimensional electrostatics by treating the system geometrically as
a "squashed wormhole" with an image charge located in a novel but obvious
position, thereby implementing a method first suggested in 1897 by Sommerfeld.
We compare and contrast the strength and location of the image charge in the
wormhole picture with that of the conventional point of view where an image
charge is located inside the circular ring. While the two viewpoints give
mathematically equivalent Green functions, we believe they provide strikingly
different physics perspectives. We also comment on earlier Green function
results by Hobson in 1900, and by Davis and Reitz in 1971, who applied
Sommerfeld's method to analyze a grounded conducting circular disk in
three-dimensional electrostatics.
