  We explore two hypotheses. First, the possibility that the quantum vacuum
energy density of the Casimir effect contributes to a (local) gravitational
vacuum energy density. Second, the possibility that a change in the
gravitational coupling implies a change in the cosmological constant. We
parametrize these two possibilities in a covariant framework and show that the
next generation of Casimir experiments does have a surprisingly good chance of
exploring this parameter space.
