  By Bernoulli's law, an increase in the relative speed of a fluid around a
body is accompanies by a decrease in the pressure. Therefore, a rotating body
in a fluid stream experiences a force perpendicular to the motion of the fluid
because of the unequal relative speed of the fluid across its surface. It is
well known that light has a constant speed irrespective of the relative motion.
Does a rotating body immersed in a stream of photons experience a
Bernoulli-like force? We show that, indeed, a rotating dielectric cylinder
experiences such a lateral force from an electromagnetic wave. In fact, the
sign of the lateral force is the same as that of the fluid-mechanical analogue
as long as the electric susceptibility is positive (\epsilon>\epsilon_{0}), but
for negative-susceptibility materials (e.g. metals) we show that the lateral
force is in the opposite direction. Because these results are derived from a
classical electromagnetic scattering problem, Mie-resonance enhancements that
occur in other scattering phenomena also enhance the lateral force.
