  Physicists have speculated about the properties of the quantum vacuum for at
least 85 years; however, only recently have they understood the quantum vacuum
sufficiently well to begin making testable predictions. Specifically, using
Maxwell's equations to describe the interaction of the electromagnetic field
with charged lepton - antilepton vacuum fluctuations, it has been possible to
calculate the permittivity of the vacuum, the speed of light in the vacuum, and
the fine structure constant. Physicists are now also beginning to successfully
address problems in cosmology based on properties of the quantum vacuum. The
terms ``vacuum catastrophe'' and ``old cosmological problem'' refer,
respectively, to the predictions that the vacuum energy density and the
cosmological constant are both approximately 120 orders of magnitude larger
than the observed values. Using properties of the quantum vacuum and
well-established physics, it is possible to demonstrate that the huge vacuum
energy cannot transfer energy to normal matter; accordingly, vacuum energy
contributes neither to the observed energy density of the universe nor to the
cosmological constant, which plays a central role in the accelerating expansion
of the universe.
