  The Copernican principle, a cornerstone of modern cosmology, remains largely
unproven at Gpc radial scale and above. Here we will show that, violations of
this type will inevitably cause a first order anisotropic kinetic Sunyaev
Zel'dovich (kSZ) effect. If large scale radial inhomogeneities have amplitude
large enough to explain the "dark energy" phenomena, the induced kSZ power
spectrum will be much larger than the ACT/SPT upper limit. This single test
confirms the Copernican principle and rules out the adiabatic void model as a
viable alternative to dark energy.
