  Is there an absolute cosmic electric potential?. The recent discovery of the
accelerated expansion of the universe could be indicating that this is
certainly the case. In this essay we show that the consistency of the covariant
and gauge invariant theory of electromagnetism is truly questionable when
considered on cosmological scales. Out of the four components of the
electromagnetic field, Maxwell's theory only contains two physical degrees of
freedom. However, in the presence of gravity, one of the "unphysical" states
cannot be consistently eliminated, thus becoming real. This third polarization
state is completely decoupled from charged matter, but can be excited
gravitationally thus breaking gauge invariance. On large scales the new state
can be seen as a homogeneous cosmic electric potential, whose energy density
behaves as a cosmological constant.
