  Zero point density fluctuations in a liquid and their potential observation
by light scattering are discussed. It is suggested that there are two distinct
effects of interest. One gives an average number of scattered photons, and
depends upon an inverse power of the photon wavelength. The second effect
arises in the scattering of finite size photon wave packets and depends upon an
inverse power of the spatial size of the wave packet. This effect appears as
large fluctuations in the number of scattered photons, and is analogous to the
vacuum fluctuations of spacetime averages of the energy density in quantum
field theory.
