  First, we present a history of the school of thought that the Cosmic
Microwave Background Radiation acts as an ether in contemporary popular
English. Then we illustrate the properties of this ether and of a hypothetical
"test mass" using a brand new thought experiment. Finally, we recount some
post-Einstein efforts at a mathematical formulation of Mach's principle and
raise some questions about what implications it has for the locality of
rotation and for quantum gravity. This paper does not prove Einstein wrong.
