  Vacuum field fluctuations exert a radiation pressure which induces mechanical
effects on scatterers. The question naturally arises whether the energy of
vacuum fluctuations gives rise to inertia and gravitation in agreement with the
general principles of mechanics. As a new approach to this question, we discuss
the mechanical effects of quantum field fluctuations on two mirrors building a
Fabry-Perot cavity. We first put into evidence that the energy related to
Casimir forces is an energy stored on field fluctuations as a result of
scattering time delays. We then discuss the forces felt by the mirrors when
they move within vacuum field fluctuations, and show that energy stored on
vacuum fluctuations contributes to inertia in conformity with the law of
inertia of energy. As a further consequence, inertial masses exhibit quantum
fluctuations with characteristic spectra in vacuum.
